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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

匯率變動對貿易, 產出之影響--國際間的實證研究

林容如, LIN, RONG-RU Unknown Date (has links)
本研究乃透過國際間各國之比較,以了解匯率變動對貿易收支與國內產生之效果。共 分成兩大部分,第一部分探討匯率變動對貿易收支的影響。根據傳統的國際收支理論 ,認為在某些情況下,一國匯率的貶值可以改善貿易收支。Miles (1979)首先 針對匯率與貿易收支的關係進行實證研究。然而,由於生產與消費有時間落後的現象 ,匯率變動對貿易的效果往往無法立即反映,甚至呈現先惡化再逐步改善的情況,一 般稱為J曲線效果。針對開發中國家是否存在J曲線效果,Bahmani-Oskooee (19 85)利用Almon 三階多項分配加以驗證。本文係根據他的模型加以延伸,文中運用 Almon 多項分配方法探討1973至1987年十個工業國家與十個開發中國家,匯 率變動對貿易收支的影響。為了估計落後期數與多項分配階數,使用兩階段的程序, 首先以Akaike提出的final prediction errer為標準,選擇最適落後期數,然後再檢 定多項分配的階數。第二部分探討匯率變動對產出的影響,依照傳統的理論,匯率貶 值會引起出口增加、進口減少,使國內產出擴充。然而Cooper(1971)觀察落後 國家資料,卻發現貶值對國內產出有緊縮效果。Edwards (1986)首先使用變異 成分分析開發中國家之匯率變動效果,本文對Edwards 的模型加以延伸,利用Almon 多項分配方法估計,檢視匯率變動是否有Cooper效果,同時比較國際間各國之差異。
102

Ett nytt ansikte utåt : <em>Ett arbete om utveckling av en B2B-sajt med en kombination av olika metoder och principer.</em> / : <em> </em>

Lundstedt, Patrik, Wass, Kristoffer January 2010 (has links)
<p>Företag som bedriver handel via nätet på sajter som inriktar sig mot privatpersoner satsar idag mycket på att utvecklas för att på bästa sätt stödja kunden mot sitt mål. Dock har företag som inriktar sig mot andra företag (B2B-business to business) inte hängt med i samma utsträckning. Den här rapporten syftade till att undersöka hur man kan arbeta för att ta fram ett designförslag på en B2B-sajt, närmare bestämt vilka metoder och teorier man kan dra nytta av. Metoder och teorier som har använts är effektkartläggning, Coopers målinriktade designmetod, Nielsens designprinciper för användbarhet och information foraging. Arbetet resulterade i en prototyp kring vilken en diskussion fördes följt av slutsatsen att valet av metoder och teorier tycks vara en lämplig kombination vid utveckling av B2B-sajter men att ytterligare forskning krävs för att skapa en enhetlig metod.</p>
103

Copper isotope compositions of Cenozoic mafic-intermediate rocks of the Northern Great Basin and Snake River plain (USA)

Maynard, Annastacia Lin January 1900 (has links)
Master of Science / Department of Geology / Matthew E. Brueseke / Mid-Miocene epithermal Au-Ag ores of the northern Great Basin USA are related to magmatism associated with the inception of the Yellowstone hotspot. The geochemical chemical connection between these ores and spatially and temporally related volcanism is not well understood, but has been suggested (Kamenov, 2007; Saunders et al., 2015). These Cu- and Pb- isotope studies show that the ore and associated gangue minerals have different sources of Pb, which supports evidence that the metal(loids) originate from a deep magmatic source (Saunders et al., 2008). Cu isotopes as a tool for exploring linkages between ore deposits and related volcanic rocks is a new and evolving field. A suite of mid-Miocene Northern Great Basin (NGB) and Snake River Plain (SRP) volcanic rocks was analyzed by aquaregia leach for their δ⁶⁵Cu compositions. These samples have all been previously characterized and include basalts, trachybasalt, basaltic andesites, and basaltic trachyandesites that are representative of regional flood basalt magmatism and younger basalt eruptions in central Idaho. Included are rocks from the Santa Rosa-Calico volcanic field, NV (e.g., Buckskin-National district); Owyhee Mountains, ID (Silver City District); Midas, NV region, near Jarbidge, NV; and a locality proximal to Steens Mountain, OR. Also included are two Pleistocene basalts from the central Snake River plain unequivocally related to the Yellowstone hotspot volcanism (McKinney Basalt and Basalt of Flat Top Butte), and one Eocene basalt from the Owyhee Mountains that is related to pre-hotspot arc volcanism. International rock standards ranging from ultramafic to intermediate were also analyzed in this study for comparison. Our new δ⁶⁵Cu data greatly expands the range of known Cu isotopic compositions for basalts, with values ranging from -0.84‰ to +2.61‰. These values overlap with the δ⁶⁵Cu of regional ores, further suggesting a link between the source(s) of the ores and the NGB rocks. The range of δ⁶⁵Cu values also overlaps with mantle rock values, suggesting that the Cu isotopic composition may be a signature derived from the mantle source. Fractionation mechanisms that cause such a broad range in Cu isotopes are still unclear but liquid-vapor transitions and mantle metasomatism are being explored. Furthermore, δ⁶⁵Cu values of international rock standards reported in this study did not agree with previously reported data (Archer and Vance, 2004; Bigalke et al., 2010; Moeller et al., 2012; Liu et al., 2014, 2015) suggesting that aquaregia leach may not be a preferable technique when analyzing volcanic rocks.
104

From Copper Zinc Tin Sulfur to Perovskites: Fabrication and Characterization of New Generation of Solar Cells

Wozny, Sarah 11 August 2015 (has links)
In 2013, the worldwide production of renewable electricity accounted for 22.1% of the total energy production with 0.9% coming from solar photovoltaics (PVs). Recently, there has been a growing interest for Cu2ZnSnS4 (CZTS) quaternary semiconductor due to the abundance and low cost of its precursors. Moreover, this chalcopyrite material has an ideal direct band gap around 1.5 eV, high absorption coefficient (α >104 cm-1) and high conductivity, making it suitable for nanostructured and dye-sensitized solar cell (DSSC) applications. Here, CZTS nanoparticles have been synthesized by pulsed laser deposition (PLD) and simultaneously deposited in the interstitial space of ZnO nanowire arrays to form bulk heterojunction 3D nanostructured solar cells. Secondly, vertically oriented CZTS nanoplates have been synthesized by PLD and used as counter electrode in platinum-free dye-sensitized solar cells. These CZTS nanostructures proved to be suitable in achieving workable solar cells, which could significantly cut down the cell cost and provide environmentally friendly photovoltaic devices. Alternately, hybrid organic–inorganic perovskite solar cells have become one of the most attractive photovoltaic technologies with easy solution fabrication and high conversion efficiencies. However, the devices remain unstable under certain processing and environmental conditions. Herein, formamidinium lead tri-halide perovskite (FAPbI3) planar heterojunction solar cells have been fabricated under a controlled environment. The fabrication parameters (precursor concentration, annealing, etc) and the effect of humidity on the structural, optical, and electrical properties of FAPbI3 thin films and devices have been investigated and proved to be critical in the processing of efficient devices. Solar cells with conversion efficiency of 16.6% have been obtained. Furthermore, in-situ techniques such as in-situ (scanning) transmission electron microscopy and in-situ XRD were performed to understand the crystallization and degradation mechanisms of FAPbI3 thin films.The in-situ data were correlated with planar heterojunction FAPbI3 devices efficiency data in order to improve the device fabrication process.
105

Phenomenological phase-fluctuation model for the underdoped cuprates / Phänomenologisches Phasenfluktuationsmodell für die unterdotierten Kuprate

Eckl, Thomas January 2004 (has links) (PDF)
In this thesis, a phenomenological phase-fluctuation model for the pseudogap regime of the underdoped cuprates was discussed. The key idea of the phase-fluctuation scenario in the high-T_c superconductors is the notion that the pseudogap observed in a wide variety of experiments arises from phase fluctuations of the superconducting gap. In this scenario, below a mean-field temperature scale T_c^{MF}, a d_{x^2-y^2}-wave gap amplitude is assumed to develop. However, the superconducting transition is suppressed to a considerably lower transition temperature T_c by phase fluctuations. In the intermediate temperature regime between T_c^{MF} and T_c, phase fluctuations of the superconducting order parameter give rise to the pseudogap phenomena. The phenomenological phase-fluctuation model discussed in this thesis consists of a two-dimensional BCS-like Hamiltonian where the phase of the pairing-amplitude is free to fluctuate. The fluctuations of the phase were treated by a Monte Carlo simulation of a classical XY model. First, the density of states was calculated. The quasiparticle tunneling conductance (dI/dV) obtained from our phenomenological phase fluctuation model was able to reproduce characteristic and salient features of recent scanning-tunneling studies of Bi2212 and Bi2201 suggesting that the pseudogap behavior observed in these experiments arises from phase fluctuations of the d_{x^2-y^2}-wave pairing gap. In calculating the single-particle spectral weight, we were further able to show how phase fluctuations influence the experimentally observed quasiparticle spectra in detail. In particular the disappearance of the BCS-Bogoliubov quasiparticle band at T_c and the change from a more V-like superconducting gap to a rather U-like pseudogap above T_c can be explained in a consistent way by assuming that the low-energy pseudogap in the underdoped cuprates is due to phase fluctuations of a local d_{x^2-y^2}-wave pairing gap with fixed magnitude. Furthermore, phase fluctuations can explain why the pseudogap starts closing from the nodal points, whereas it rather fills in along the anti-nodal directions and they can also account for the characteristic temperature dependence of the superconducting (pi,0)-photoemission-peak. Next, we have shown that the "violation" of the low-frequency optical sum rule recently observed in the SC state of underdoped Bi2212, which is associated with a reduction of kinetic energy, can be related to the role of phase fluctuations. The decrease in kinetic energy is due to the sharpening of the quasiparticle peaks close to the superconducting transition at T_c == T_{KT}, where the phase correlation length xi diverges. A detailed analysis of the temperature and frequency dependence of the optical conductivity sigma(omega)=sigma_1(omega)+i sigma_2(omega) revealed a superconducting scaling of sigma_2(omega), which starts already above T_c, exactly as observed in high-frequency microwave conductivity experiments on Bi2212. On the other hand, our model was only able to account for the characteristic peak, which is observed in sigma_1(omega) close to the superconducting transition, after the inclusion of an additional marginal-Fermi-liquid scattering-rate in the optical conductivity formula. Finally, we calculated the static uniform diamagnetic susceptibility. It turned out that the precursor effects of the fluctuating diamagnetism above T_c are very small and limited to temperatures close to T_c in a phase-fluctuation scenario of the pseudogap. Instead, the temperature dependence of the uniform static magnetic susceptibility is dominated by the Pauli spin susceptibility, which displayed a very characteristic temperature dependence, independent of the details of the gap function used in our model. This temperature dependence is qualitatively very similar to the experimentally observed change of the Knight-shift as a function of temperature in underdoped Bi2212. / In der vorliegenden Arbeit wurde ein phänomenologisches Phasenfluktuationsmodell zur Beschreibung der "Pseudolücken"-Phase in den unterdotierten Hochtemperatur-Supraleitern untersucht. Im Gegensatz zu konventionellen metallischen BCS-Supraleitern skaliert in den unterdotierten Kupraten die kritische Temperatur, unterhalb derer Supraleitung einsetzt, nicht mit der Größe der supraleitenden Energielücke Delta, und damit der Stärke der Paaranziehung, sondern mit der superfluiden Dichte rho_s, d. h. der Dichte der supraleitenden Elektronen. Unterdotierte Kuprate liegen im Phasendiagramm sehr nahe am Mott-isolierenden Zustand und haben daher eine relativ geringe Anzahl an beweglichen Ladungsträgern. Dies hat zur Folge, dass bei einer Temperatur T^* = T_c^{MF} zunächst die Paarung der Ladungsträger einsetzt, diese sich aber erst bei einer sehr viel niedrigeren Temperatur T_c = T_{phi} phasenkohärent bewegen und damit supraleitend werden. Dies ist das so genannte Phasenfluktuationsszenario für die Pseudolücke im Energiespektrum der unterdotierten Kuprate. Die Pseudolücke entwickelt sich oberhalb von T_c kontinuierlich aus der supraleitenden Energielücke heraus und wird bis zu einer Temperatur T^* >> T_c in verschiedenen Experimenten beobachtet. Als Ausgangspunkt der vorliegenden Arbeit diente nun ein BCS-artiger Hamiltonoperator mit fester Paarungsamplitude, bei dem jedoch die Phase der lokalen Paare frei fluktuieren konnte. Alle Rechnungen wurden durchgeführt, indem mittels einer Monte Carlo Simulation des klassischen XY-Modells verschiedene Phasenkonfigurationen erzeugt wurden und für jede dieser Phasenkonfigurationen der BCS-artige Hamiltonoperator exakt diagonalisiert wurde. Die erste Anwendung dieses phänomenologischen Phasenfluktuationsmodells bestand in der Berechnung von Einteilchen-Tunnelspektren. Hierbei konnte eine ausgezeichnete Übereinstimmung mit den Experimenten, insbesondere was die Temperaturentwicklung der supraleitenden Kohärenzpeaks und das charakteristische auffüllen der Pseudolücke mit ansteigenden Temperaturen betrifft, erzielt werden. Durch einen detaillierten Vergleich zwischen Theorie und Experiment konnte gezeigt werden, auf welche Weise Phasenfluktuationen das Quasiteilchenspektrum beeinflussen. Insbesondere das Verschwinden der BCS-Bogoliubov Quasiteilchenbänder oberhalb von T_c und die Veränderung der Energielücke, von einer V-artigen supraleitenden Lücke hin zu einer mehr U-artigen Pseudolücke oberhalb von T_c, konnte in konsistenter Weise durch Phasenfluktuationen des supraleitenden Ordnungsparameters erklärt werden. Darüberhinaus war das Phasenfluktuationsmodell in der Lage zu erklären, warum die Pseudolücke von den Knotenpunkten an der Fermifläche her anfängt sich zu schließen, wohingegen sie an den Anti-Knotenpunkten eher aufgefüllt wird. Auch konnte die charakteristische Temperaturentwicklung des so genannten "supraleitenden" (pi,0)-Photoemissionspeaks sehr gut durch Phasenfluktuationen beschrieben werden. Als nächstes wurden Experimente zur Verletzung der optischen Niederfrequenz-Summenregel in unterdotierten Bi2212-Verbindungen untersucht, welche auf eine Reduktion der kinetischen Energie im supraleitenden Zustand hindeuten. Es konnte gezeigt werden, dass diese Reduktion mit der Rolle von Phasenfluktuationen beim supraleitenden Übergang in Verbindung gebracht werden kann. Die Reduktion der kinetischen Energie erfolgt durch das Entstehen scharfer Quasiteilchenpeaks bei T_c. Dort beginnt die Korrelationslänge der fluktuierenden Phasen zu divergieren, und es stellt sich eine quasi-langreichweitige Ordnung ein. Eine detailliert Analyse der Frequenz und Temperaturabhängigkeit der optischen Leitfähigkeit ergab eine supraleitende Skalierung des Imaginärteils der optischen Leitfähigkeit schon oberhalb von T_c, genau wie in Mikrowellen-Hochfrequenzleitfähigkeitsexperimenten beobachtet. Das experimentell beobachtete Maximum im Realteil der optischen Leitfähigkeit bei T_c konnte unser phänomenologisches Phasenfluktuationsmodell jedoch nur durch den Einbau einer zusätzlichen marginalen Fermiflüssigkeits-Streurate in die Formel für die optische Leitfähigkeit beschreiben. Als letztes wurde die homogene statische diamagnetische Suszeptibilität berechnet. Es stellte sich heraus, dass Vorläufereffekte des idealen diamagnetischen Zustands oberhalb von T_c in der statischen diamagnetische Suszeptibilität äußerst gering sind und sich auf Temperaturen in der Nähe von T_c beschränken. Stattdessen wird die Temperaturabhängigkeit der statischen homogenen magnetischen Suszeptibilität von der Pauli-Spinsuszeptibilität bestimmt. Diese zeigt für das Phasenfluktuationsmodell einen charakteristischen Verlauf, der erstaunlich gut mit der Temperaturabhängigkeit des Magnetresonanz Knight-shift in unterdotierten Bi2212-Verbindungen übereinstimmt.
106

Antebellum Writer-Travelers and American Cosmopolitanism

Iannucci, Alisa Marko January 2011 (has links)
Thesis advisor: James D. Wallace / James Fenimore Cooper, George Catlin, and Margaret Fuller all spent significant portions of their lives living outside the United States, among people who - at least initially - were foreign to them. The writing those cross-cultural forays inspired demonstrated that they learned a great deal about American culture in addition to the foreign cultures they visited, and that sometimes the insights gained were difficult to hear but impossible to refute. These writers became advocates for a cosmopolitan approach not only to travel but also to cultural identity. Each felt the slipperiness of U.S. cultural identity and determined that the most productive means of securing it was by active cosmopolitan engagement with foreign others. This project explores how travel led them to view culture as a moveable category, and as a result, to work proactively to encourage a culture of patriotic cosmopolitanism in the United States. While Fuller, Cooper, and Catlin lived and wrote, the United States was marked by an isolating insistence on exceptionalism that dominated American culture. Calls for transformative, active, or personal engagement with foreign cultures were rare. Juxtaposing Appiah's approach to cosmopolitanism with the cultural analysis of such critics as William W. Stowe and Mark Renella on travel and nineteenth-century American culture, and Larry J. Reynolds and Michael Paul Rogin, on political issues of the same era gives a new perspective to these writers. Catlin, Cooper, and Fuller were dissimilar in many ways, but all enacted a cosmopolitanism that was unusual for their time and striking in its opposition to nationalist cultural currents. Their careers were defined by travel experiences marked by challenges to their cultural identity, and they met these with self-reflection that led to their awareness of the treatment cultural others received from Americans. Engaging with both Amerindian and European versions of "foreignness" led these writers to preach a cosmopolitan consciousness and to model the best ways for Americans to comport themselves while acting as citizen diplomats. A close reading of Catlin's presence as cultural intermediary in his ethnography reveals a man seeking to meet Amerindians on their own terms; he was a rare case study, and the lukewarm support he received is telling; mainstream Americans were not interested in viewing Indians as living people with a culture worth learning about. Most important, Catlin's writings of his experience in Indian lands and abroad demonstrate his exceptional receptivity to foreignness. Catlin did not see or market himself as a "travel-writer" but rather an artist and advocate for the Indians offering his own brand of proto-ethnography to the nineteenth-century reading public. Nevertheless, his work is an unusual addition to the travel-writing genre, and particularly productive in its presentation of how one adventurous traveler's experience of cultural difference led to cosmopolitan awareness. The extent to which one's experience of a foreign culture can be communicated to others who have not shared in those experiences is limited, and this accounts, in part, for the contradictions, defensive rationalizations, and rambling reflections present in Catlin's accounts. He faced a task that travel writers who direct their work to home-bound readers can't avoid: the unacknowledged naiveté of such readers must be dealt with, and foreignness presented in terms of the known. The psychological processes undergone by cross-cultural travelers can be significant, and are not so easily translated to the uninitiated. Cooper recognized that cross-cultural encounters had formed American identity from the start and worked against the prevailing tendency to denigrate, dismiss, and destroy Amerindians. He noticed that efforts to encourage international acceptance of American culture as a distinctive, worthy addition to the catalog of world cultures were often hampered by cross-cultural missteps and failures. More than most, Cooper understood the process of exploring foreignness as well as the value of the experience, but found that understanding difficult to communicate to less-cosmopolitan audiences. Cooper's cross-cultural engagement is explored in two works that participated in the ongoing transatlantic squabble over the insinuations about U.S. culture in travel writing by Europeans. In Notions of the Americans (1828) and "Point de Bateaux à Vapeur--Une Vision" (1832), Cooper advanced American arguments against the propriety and usefulness of such judgments. Homeward Bound and Home As Found (1838), took these transatlantic discussions to a different level. Remaining staunchly American, Cooper was less interested in defending his country from European "attacks" than in understanding the differences that inspired them; his argument, aimed at Americans, was for a more enlightened U.S. culture--one that had the cosmopolitan skills required to command respect internationally. Cooper's ultimate understanding of "culture" as a moveable category of human difference in The Monikins (1835). Fuller worked for a cosmopolitan American culture that would be able to lead the world for the sake of the progress of humanity. Americans would be simultaneously citizens of the United States and of the world. Through her engagement with other cultures, she sought to fit her own to her ideal. Hers was not a consuming globalism, but a model of international engagement from the ground up. By extending the transcendental opposition to individual conformity to the cultural scale, Fuller hoped that thinking Americans would learn to benefit from the "variety" that surrounded them. In her writing and by her example, she shifted the focus of travel from place to people, urging Americans to travel not only to see foreign places but to meet foreign people and immerse themselves in foreign points of view. She relates her impressions of Native Americans as foreigners who suffer from Americans' failure to see them as a people worthy of respectful engagement, and her desire that her country not repeat that mistake in dealing with other nations. In her first significant travel experience, which exposed her to immigrant settlers and Indian communities, she discovered her interest in learning about and forming relationships with groups of people who were different from her, displaying not only cosmopolitan curiosity but cosmopolitan willingness to put herself forward into the unknown. Her years of study of foreign language and arts had left her better prepared to make meaningful connections there. As a woman she felt especially well-positioned to practice a cosmopolitanism that was its own kind of revolution. / Thesis (PhD) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: English.
107

Interações magnéticas em sais de (cobre-dipeptídeos): Cu2+: Gly-Trp e Cu2+: Trp-Gly / Magnetic interactions in copper model systems Cu2+:Gly-Trp and Cu2+: Trp-Gly

Costa Filho, Antonio José da 18 March 1997 (has links)
Derivados metálicos de aminoácidos são sistemas modelo simples para o estudo de íons metálicos em estruturas que simulam proteínas. O principal objetivo dessas investigações é avaliar as magnitudes dos parâmetros de acoplamento por interação de troca e relacioná-Ias aos caminhos químicos de supertroca. Foram realizadas medidas através da técnica de Ressonância Paramagética Eletrônica (RPE) em mono cristais dos compostos Cu2+:Gly-Trp e Cu2+:Trp-Gly, nas frequências 9,3 e 33GHz e à temperatura ambiente. Ambos os complexos estão no grupo espacial P212121, com quatro moléculas quimicamente idênticas, mas magneticamente não equivalentes, por cela unitária (Z=4). Essas moléculas formam duas subredes (1 e 2) acopladas por uma interação de troca inter-rede. Cada subrede contem dois íons de cobre não equivalentes, acoplados por uma interação de troca intra-rede. O composto Cu2+:Gly-Trp apresenta duas linhas parcialmente resolvidas em algumas direções do campo magnético aplicado no plano ac, ao passo que há apenas uma linha para todas as orientações nos outros dois planos cristalográficos. O desacoplamento dos espectros leva aos fatores-g moleculares. g&#8869;=2,0554(3) e g//=2,2086(7) (Cu2+:Gly-Trp). Os espectros de RPE mostram apenas uma linha para todas as direções de campo nos três planos cristalográficos para o Cu2+:Trp-Gly. Portanto, os eixos principais magnéticos são os eixos cristalográficos e a decomposição não é possível através de métodos matemáticos. Medidas utilizando um mono cristal de Zinco (Zn2+:Trp-Gly) ou frequências mais altas (90GHz) podem ajudar na solução desse problema. Os fatores-g moleculares para o composto Cu2+:Trp-Gly foram, então, tomados como sendo aqueles determinados previamente através de medidas em solução aquosa do mesmo composto por M.C.Lara et al. Os dados de RPE juntamente com a teoria de Kubo- Tomita permitem avaliar os acoplamentos intra-rede (J(1)) e inter-rede (J(1,2)) por interação de troca. Os seus valores são /J(1)/I =53,7mK e /J(1,2 /I =7,lmK para o Cu2+:Gly-Trp e /J(1)/=990mK e /J(1,2)/=48,4mK para o Cu2++:Trp-Gly. Eles são discutidos em termos da estrutura cristalina dos compostos, sendo os caminhos para transferência eletrônica constituídos por pontes de hidrogênio e interações cátion-&#960; para o Cu2+:Gly-Trp, e ligações químicas covalentes e interações cátion-&#960; para o Cu2+ +:Trp- Gly. Os valores calculados para /J(1)/ no composto Cu2+: Gly- Trp e /J(1,2)/ no Cu2+:Trp-Gly são uma boa estimativa da magnitude do acoplamento mediado por interações cátion-&#960;. / Metal derivatives of amino acids are simple model systems to study properties of metal ions in protein-like structures. The main purpose of those investigations is to evaluate the magnitudes of exchange coupling parameters and correlate their values with the chemical paths for superexchange. Electron Paramagnetic Resonance (EPR) measurements have been performed in single crystals of the compounds Cu2+:Gly-Trp and Cu2+:Trp-Gly at 9.3 and 33GHz, at room temperature. Both complexes crystallize in the space group P212121, with four chemically identical but magnetically non-equivalent molecules per unit cell (Z=4). These molecules are arranged in two subsets (1 and 2) coupled by an intersubset exchange coupling. Each subset contains two non-equivalent and interacting copper ions (intrasubset exchange coupling). The compound CU2+:Gly-Trp has two partially resolved lines for some field directions in the ac plane, while there is on1y one line along any direction in the other two crystallographic planes. The decoupling of the spectra leads to g&#8869;=2,0554(3) and g//=2,2086(7) molecular g-factors (Cu2+:Gly-Trp). The EPR spectra show only one line for all field directions in the three crystallographic planes for Cu2+:Trp-Gly. Then, the magnetic principal axes are the crystallographic axes and the g-factor decomposition is not possible by mathematical methods. Measurements of a Zinc (Zn2+:Trp-Gly) single crystal or measurements using high microwave frequencies (90GHz) may help to solve this problem. The molecular g-factors for the compound Cu2+:Trp-Gly were taken to be those ones determined previously from aqueous solution measurements of the same complex by M.C.Lara et al. The EPR data used in conjunction with the Kubo and Tomita\'s theory allow to evaluate the intrasubset (J(1)) e intersubset (J(1,2)) exchange interaction parameters. Their values are /J(1)/ =53,7mK and /J(1,2)/=7,lmK for Cu2+:Gly-Trp and /J(1)/=990mK and /J(1,2)/=48,4mK for Cu2+:Trp-Gly. They have been discussed in terms of the crystal structure of the compounds, and the paths for electron transfer are determined as hydrogen bonds and cation-&#960; interactions for Cu2+:Gly-Trp, and a covalent chemical bond and cation-&#960; interactions for Cu2+:Trp-Gly. The values evaluated for the /J(1)/ in Cu2+:Gly-Trp e /J(1,2)/ in Cu2+:Trp-Gly are a good estimative for the magnitude of the cation-&#960; interactions.
108

Comportamento do cobre aplicado no solo por calda bordalesa / Behavior of copper applied to soil through bordeaux mixture

Felix, Fabiana Ferreira 29 July 2005 (has links)
Apesar da preocupação atual com a contaminação do ambiente, pelo uso agrícola de resíduos industriais e urbanos, metais pesados podem ser incorporados ao solo por práticas agrícolas tradicionais como uso de fertilizantes e defensivos. Objetivando avaliar o comportamento do cobre aplicado ao solo através de calda bordalesa foram conduzidos ensaios nos quais o fungicida foi aplicado ao solo acondicionado em colunas, bem como consideradas amostras de solo sob cultura de frutíferas. A mobilização do Cu foi estudada em experimento com colunas de lixiviação, feitas de tubos de cloreto de polivinil (PVC), utilizando dois tipos de solos: Latossolo Vermelho eutroférrico (LVef) e Latossolo Vermelho Amarelo distrófico típico (LVAd). O cobre aplicado por um material alcalino como a calda bordalesa é relativamente imóvel no solo, mas pressupõe-se que poderá ser mobilizado pela ação de compostos orgânicos que atuam como complexantes. Desta forma, foram aplicados como compostos orgânicos: dois materiais de uso generalizado na agricultura (esterco de galinha e torta de filtro); um material sintético de elevado poder complexante (NaH2EDTA) e citrato de amônio para representar os agentes quelantes de ocorrência natural no ambiente. Em adição ao experimento em colunas, para determinar as frações de cobre presente no solo, foram coletadas amostras de solo na profundidade de 0-20 cm, no município de Louveira, Estado de São Paulo, em pomares de frutíferas onde se usa rotineiramente calda bordalesa como fungicida. Nesses locais, o teor de Cu do solo extraído por DTPA variou entre 6,5-34,3 mg Cu kg-1, enquanto que o teor de Cu total variou entre 40,8-108,8 mg kg-1. Para avaliar a disponibilidade do Cu nos solos de Louveira e nos solos do experimento em colunas foi escolhido o método de Neubauer, pela vantagem de ser um método biológico de determinação da quantidade disponível de elementos no solo. A lixiviação na coluna do solo LVAd, onde foi aplicado o EDTA, conseguiu mobilizar 436,5 µg de Cu, massa que representa uma fração muito pequena do cobre total aplicado ao solo por meio da calda bordalesa. Trata-se, entretanto, de um valor bastante significativo frente ao que foi removido nos demais tratamentos. Embora quase não tenha sido mobilizado cobre para fora das colunas, os resultados da análise química do solo indicaram a movimentação do cobre dos segmentos superiores para os inferiores, sob a ação dos tratamentos, na faixa de 5,0-48,2 mg Cu. Quanto à absorção de cobre pelas plantas no experimento de Neubauer, observou-se que a aplicação do EDTA favoreceu a absorção do cobre pelas plantas de arroz em ambos os solos estudados, entretanto não influenciou na massa seca das plantas. Já nas amostras dos solos de Louveira a absorção de cobre diminuiu a massa seca das plantas, tanto quando se considerou a concentração de cobre no tecido vegetal como a massa total de cobre absorvido. O Cu absorvido pelas plantas também se correlacionou com teores de cobre trocável, cobre ligado a carbonato e cobre ligado a óxidos de Fe e Mn, obtidos no estudo de fracionamento. O extrator DTPA mostrou ainda ser um bom indicador da disponibilidade de cobre aplicado pela calda bordalesa. / Despite the current concerns regarding the environment contamination by the agricultural use of industrial and urban wastes, heavy metals can be incorporated to the soil through traditional fertilizers and defensives. Aiming to evaluate the behavior of copper applied to the soil through the Bordeaux mixture, trials were carried out in which the fungicide was applied to the soil packed in columns, as well as samples of soil under fruit cultures were considered. The mobilization of Cu was studied in experiments with leaching columns, which consisted of polyvinyl chloride tubes (PVC), using two types of soil: Latossolo Vermelho eutroférrico (LVef) e Latossolo Vermelho Amarelo distrófico típico (LVAd). Copper applied through an alkaline material such as the Bordeaux mixture is relatively immobile in the soil but it is expected to be mobilized by the action of organic complexing compounds. This way they were applied as organic compounds, two materials generally used in agriculture: poultry manure and filter cake; a synthetic material with high affinity for metals (NaH2EDTA) and ammonium citrate in order to represent the ligants of wide spread occurrence in the environment. In addition to the experiment in columns and to determine the fractions of copper present in the soil, 0-20 cm samples of soil were collected in grape and fig orchard located in the city of Louveira , SP, where the Bourdeaux mixture is commonly used as a fungicide. Is these places the total copper content of the soil extracted by DTPA varied between 40,8-108,8 mg kg-1. To evaluate the availability of copper in the soil of Louveira, and in the soils of the column experiment, the Neubauer method was chosen due to the advantage of being a biological method of determination of the available amount of elements in the soil. The leaching in the LVAd soil column, where EDTA was applied was able to mobilize 436,5 µg of cu, mass that represents a very small fraction of the total copper applied to the soil through the Bordeaux mixture. It refers to, subconsequently to a very significant amount when compared to the quantity obtained through other methods. Although almost no copper was removed out of the columns, the results of the chemical analysis indicated the movement of copper from the upper segments to the lower segments, under the action of treatments, the range of 5-48,2 mg of copper. Regarding the absorption of copper by plants in the Neubauer experiment it was observed that the application of EDTA favored the absorption of copper by the rice plants, in both studied soil, however it didn’t influence the dry mass of plants. In the soil samples from Louvreira, the copper absorption diminished the total dry mass of the plants, when considered the copper concentration in the vegetal tissue, as well as the total content of copper absorbed. The copper absorbed by the plants was correlated to exchangeable copper content as well as copper linked to carbonate and copper linked to oxides of Fe and Mn, obtained through the fractioning study. The DTPA extractor proved to be a good indicator of the availability to plants of copper applied through the Bordeaux mixture.
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Educação transvalorizada e as iniciativas que brotam em meio às formas dominantes de organização

Griner, Almog January 2017 (has links)
As escolas de hoje possuem ainda forte herança da revolução industrial, com um viés assistencialista, visando “guardar” as crianças e prepará-las para o mercado de trabalho. No entanto, há escolas que buscam fugir deste modelo, encontrando em seu caminho fortes pressões homogeneizantes, seja de parâmetros curriculares de órgãos governamentais, de pressões mercadológicas e, até mesmo, dos pais de seus alunos. Mesmo existindo tais pressões, algumas escolas ainda desenvolvem a sua autonomia, encontrando práticas de gestão e educação próprias. Essa pesquisa busca olhar estas práticas – que demonstram aspectos de unicidade das escolas –, propondo-se a observar como emerge o novo em um ambiente marcado predominantemente por um pensamento tradicional, burocrático e empresarial. Para embasar esta análise, trazemos alguns elementos teóricos. Em primeiro lugar, discute-se o momento da educação no Brasil, questionando a lógica instrumental predominante a partir das visões de autores como Guerreiro Ramos, Tragtenberg e Prestes Motta. Em seguida, para analisar o surgimento de novas ações e práticas de gestão e educação, nos fizemos valer de autores que se pautam em uma abordagem processual, utilizando, portanto, o conceito de Campo Aberto de Robert Cooper (1976). O autor nos oferece a possibilidade de observar as organizações de forma mais compreensiva, em seus momentos de estrutura e processo, permitindo perceber como se dá a criação do novo. Como se resgatam coisas que estão em sua não forma, no latente, abstratas para o universo concreto, real, a circunstância literal. Isso se dá a partir das crises, rupturas, acasos, modelos abertos de mudança, como crescem e se desenvolvem os projetos de forma natural – da projeção à construção –, ou fazendo um caminho inverso Foi a partir desse subsídio teórico que esse estudo buscou três escolas brasileiras para conhecer e observar: Escola Waldorf Querência, em Porto Alegre – RS; Oga Mitá, no Rio de Janeiro – RJ; e Casa Escola, em Natal – RN. Para a análise de cada uma dessas escolas – que compuseram um estudo de casos múltiplos –, foram utilizados dados secundários a partir de pesquisa documental e dados primários coletados a partir de observação participante, diários de campo, entrevistas abertas e entrevistas semiestruturadas realizadas em três períodos: novembro e dezembro de 2016 na Escola Waldorf Querência; fevereiro e março de 2017 na Oga Mitá; e maio de 2017 na Casa Escola. Através da análise dos dados coletados, com o auxílio do software Nvivo, observou-se que as escolas estudadas valorizam o aspecto humano da educação, respeitando a individualidade dos alunos, assim como o cuidado com os profissionais da escola e os familiares dos estudantes. As três escolas mostram-se bastante abertas ao diálogo e à participação – de diferentes formas e intensidades Observou-se, ainda, que as práticas desenvolvidas nestas escolas repercutem na comunidade escolar fazendo com que haja, muitas vezes, uma ressignificação de sua compreensão do que é escola, que passa a ser visto como algo mais amplo e prazeroso. Por fim, ao se analisarem como surgem as práticas inovadoras, percebeu-se que estas escolas não se prendem tanto às imagens prévias e aos padrões, mostrando abertura para a emergência de novas práticas através de momentos de ruptura, crises, acasos, mudanças abertas, dentre outros, em uma clara alternância entre períodos de maior propensão à estrutura e outros que se inclinam ao processo. Ao analisarmos os casos da Querência, Casa Escola e Oga Mitá, percebemos que os novos elementos, práticas e ações que caracterizam estas escolas e as tornam diferentes das instituições que seguem linhas tradicionais, emergem dada sua capacidade de abrir-se à mudança, mantendo espaços de resistência ao mesmo tempo em que equilibram pressões diversas para conformarem-se. / Schools today still possess a great heritage from the industrial revolution, with an assistentialist bias, aiming to “keep” the children and preparing them to the workplace. However, there are schools that aim to escape from such model, finding in their path a great deal of homogenizing pressure, from obligatory curriculums issued by the state, education market and even from parents of students. Even with such pressures, a few schools manage to develop some autonomy, creating their own personal practices of management and education. This research aims to investigate such practices – which demonstrate unique aspects of the schools –, observing how new practices emerge in an environment marked predominantly by a traditional, bureaucratic and business mindset. To base our analysis, we bring different theoretical elements. First, we discuss the moment of education in Brazil, questioning the predominant instrumental logic from the point of view of authors such as Guerreiro Ramos, Maurício Tragtenberg and Prestes Motta. Second, to analyze the emergence of new actions and practices in management and education, we make use of authors that use an approach based on process philosophy, mainly the Open Field concept from Robert Cooper (1976). Cooper offers us the possibility to observe organizations in a more comprehensive manner, in its moments of structure and process, allowing us to perceive the emergence of novel actions and practices; how to rescue things that are still potential, latent, abstract to the concrete, real universe. This happens through crisis, ruptures, chance, open models of change, which grow and develop the projects naturally – from projection to construction –, or making the inverse path. develop the projects naturally – from projection to construction –, or making the inverse path. It was from this theoretical subsidy that this study looked for three Brazilian schools to visit and observe: Querência Waldorf School, in Porto Alegre (RS), Oga Mitá, in Rio de Janeiro (RJ), and Casa Escola, in Natal (RN). To analyze each school – as a multiple case study – secondary data was used from documental research and primary data was collected from participant observation, research diaries, and open and semi-structured interviews in the following periods: November and December 2016 at Waldorf Querência; February and March 2017 at Oga Mitá and May of 2017 at Casa Escola. Through analysis of collected data using Nvivo software, it was observed that these schools value the human aspect of education, respecting students’ individuality, and caring for their professionals and the family of the students. The three schools were shown to be very open to dialogue and participation – in different ways and intensities. It was observed, also, that the practices developed in these schools reverberate through the school community creating in many cases a change in the comprehension of what a school is, becoming something broader and more positive Finally, while analyzing how innovative practices emerge, it was perceived that this schools do not fixate excessively in past images and patterns, showing an opening to the emergence of new practices through moments of rupture, crisis, chances, planned open changes, among others, in a clear interchange between moments closer to a structure and others closer to process. When analyzing the cases of Querência, Casa Escola and Oga Mitá, we perceive that new elements, practices and actions that characterize these schools and make them different from more traditional institutions emerge from their capacity to remain open to change, keeping spaces of resistance at the same time in which they balance many pressures to conform.
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A evolução criadora de Bergson : fundamentos da abordagem processual das organizações?

Horbach, Gustavo Bastide January 2010 (has links)
O presente estudo tem como objetivo analisar as abordagens interpretativa e processual dos Estudos Organizacionais, expressas nas obras de seus principais autores – Karl Weick e Robert Cooper, discutindo sua relação com a filosofia do processo de Henri Bergson. Esta análise é executada no intuito de que, em se verificando uma aproximação entre estas abordagens e a filosofia bergsoniana – seus conceitos pilares e o método intuitivo – seja possível vislumbrar uma teoria do conhecimento em base processual, uma “epistemologia do processo”. A motivação para realização deste estudo deu-se por duas principais razões. A primeira é decorrente do meu próprio estranhamento e interesse, seguido de questionamentos que me levaram ao aprofundamento nas propostas destas abordagens e nas leituras dos seus principais autores. A segunda é que, em executando esta aproximação com a filosofia de Bergson e vislumbrando uma teoria do conhecimento em base processual, a negligência com que estas abordagens são tratadas dentro da área dos Estudos Organizacionais dominantes (mainstream) seja diminuída. A referência utilizada para a execução do trabalho dirigiu-se, em função da sua própria natureza, para a hermenêutica – mais especificamente para a hermenêutica filosófica de Hans-Georg Gadamer, que permite uma interpretação geradora de conhecimento político-moral engajado e preocupado. Por fim, o trabalho apresenta as considerações e os resultados da análise das abordagens processuais à luz da filosofia de Bergson, verificando que, embora estas abordagens entendam a realidade como processual, elas carecem de alinhamento ontológico e epistemológico com a filosofia do processo bergsoniana. Entretanto, ao entender e compreender a realidade sob a ótica do processo, denotando uma axiologia processual, ambas as abordagens abrem possibilidades interessantes para o reposicionamento das Teorias Organizacionais. Estas possibilidades permitirão discutir a falácia da centralidade, armadilha positiva e funcional que os Estudos Organizacionais são tentados a assumir quando entendem o processo e o movimento não como algo natural e constante, mas como exceção e hiato. / This study aims to analyze the processual and interpretative approach of Organisational Studies, expressed in the writings of its main authors - Karl Weick and Robert Cooper, discussing its relationship to the process philosophy of Henri Bergson. This analysis is performed in order that, in noting a connection between these approaches and Bergson’s philosophy - his core concepts and the intuitive method - it is possible to envision a theory of knowledge on a processual basis, an "epistemology of the process." The motivation for this study had two main reasons. The first is due to my own amazement, followed by questions that led me to go deeper on the proposals of these approaches and readings of its main authors. The second is that in executing this approach with the philosophy of Bergson, and overlooking a theory of knowledge on a processual basis, the neglect that these approaches are treated within the area of Organisational Studies (mainstream) could be decreased. The reference used for the execution of the study was, on according to its own nature, the hermeneutics – specifically the hermeneutical philosophy of Hans-Georg Gadamer, which allows the generation of a moral-political knowledge, engaged and positioned (Schwandt , 2003). Finally, the study presents the findings of the analysis of the processual approach to the philosophy of Bergson, noting that although these approaches understand reality as process, they lack ontological and epistemological alignment with the process philosophy of Bergson. However, in understanding and comprehending the reality from a process perspective, denoting an axiology of process, both approaches open up exciting and interesting possibilities for the repositioning of Organisational Theories. These possibilities will discuss the fallacy of centrality, the positive and functional trap that Organisational Studies are tempted to fall when understanding the process and the movement as something not natural and not constant, but as exception and hiatus.

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