Zugl.: Frankfurt (Main), Univ., Diss., 2004 u.d.T.: Hess, Sabine: Au pairs als postmoderne Dienstmädchen

Habilitationsschrift--Philosophische Fakultät I--Universität Zürich, 1987. / Bibliogr. p. 499-530. Index.

The thesis focuses on the area of copper twisted pair based wireline communications. As one of the most widely deployed communication media, the copper twisted pair cable plays an important role in the communication network cabling infrastructure. This thesis looks to exploit diversity to improve twisted pair channels for data communications in two common application areas, namely Ethernet over Twisted Paris and digital subscriber line over twisted pair based telephone network. The first part of the thesis addresses new approaches to next generation Ethernet over twisted pair cable. The coming challenge for Ethernet over twisted pair cable is to realise a higher data rate beyond the 25/40GBASE-T standard, in relatively short reach scenarios. The straight-forward approaches, such as improving cable quality and extending frequency bandwidth, are unlikely to provide significant improvement in terms of data rate. However, other system diversities, such as spectrum utilization are yet to be fully exploited, so as to meet the desired data rate performance. The current balanced transmission over the structured twisted pair cable and its parallel single-in-single-out channel model is revisited and formulated as a full-duplex multiple-in-multiple-out (MIMO) channel model. With a common ground (provided by the cable shield), the balanced transmission is converted into unbalanced transmission, by replacing the differential-mode excitation with single-ended excitation. In this way, MIMO adoption may offer spectrum utilization advantages due to the doubled number of the channels. The S-parameters of the proposed MIMO channel model is obtained through the full wave electromagnetic simulation of a short CAT7A cable. The channel models are constructed from the resulting S-parameters, also the corresponding theoretical capacity is evaluated by exploiting different diversity scenarios. With higher spectrum efficiency, the orthogonal-frequency-division-multiplexing (OFDM) modulation can significantly improve the theoretical capacity compared with single-carrier modulation, where the channel frequency selectivity is aided. The MIMO can further enhance the capacity by minimising the impact of the crosstalk. When the crosstalk is properly handled under the unbalanced transmission, this thesis shows that the theoretical capacity of the EoTP cable can reach nearly 200GBit/s. In order to further extend the bandwidth capability of twisted pair cables, Phantom Mode transmission is studied, aiming at creating more channels under balanced transmission operation. The second part of the thesis focuses on the research of advanced scheduling algorithms for VDSL2 QoS enhancement. For VDSL2 broadband access networks, multi-user optimisation techniques have been developed, so as to improve the basic data rate performance. Spectrum balancing improves the network performance by optimising users transmit power spectra as the resource allocation, to mitigate the impact from the crosstalk. Aiming at enhancing the performance for the upstream VDSL2 service, where the users QoS demand is not known by all other users, a set of autonomous spectrum balancing algorithms is proposed. These optimise users transmit power spectra locally with only direct channel state information. To prevent selfish behaviour, the concept of a virtual user is introduced to represent the impact on both crosstalk interference and queueing status of other users. Moreover, novel algorithms are developed to determine the parameters and the weight of the virtual user. Another type of resource allocation in the VDSL2 network is crosstalk cancellation by centralised signal coordination. The history of the data queue is considered as a time series, on which different smooth filter characteristics are investigated in order to investigate further performance improvement. The use of filter techniques accounts for both the instantaneous queue length and also the previous data to determine the most efficient dynamic resource allocation. With the help of this smoothed dynamic resource allocation, the network will benefit from both reduced signalling communication and improved delay performance. The proposed algorithms are verified by numerical experiments.

Made available in DSpace on 2014-06-11T19:25:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-24Bitstream added on 2014-06-13T19:32:37Z : No. of bitstreams: 1 cardoso_tr_me_guara.pdf: 1016979 bytes, checksum: e22b97fead10209e15852a61078f65bf (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O formalismo de primeira ordem de Du n-Kemmer-Petiau (DKP) descreve partículas de spin 0 e spin 1 e tem sido utilizado na análise de interações relativísticas de hádrons com núcleos como uma alternativa para análise baseada nos formalismos de segunda ordem convencionais de Klein-Gordon e Proca. Apresentamos a equação geral de DKP, discutimos as condições sobre as interações que levam a uma corrente conservada e os efeitos das transformações de paridade, conjugação de carga e reversão temporal. Adotando uma representação especí ca para as matrizes de DKP, estabelecemos as equações de movimento para os componentes do espinor de DKP na presença das interações escalares e vetoriais. Salientamos que o componente espacial do potencial vetorial não-mínimo não pode ser absorvido no espinor. Mostramos que o componente espacial do potencial vetorial não-mínimo poderia ser irrelevante para a formação de estados ligados para potenciais que se anulam no in nito mas que a sua presença é uma condição sine qua non para o con namento. Algumas aplicações em potenciais unidimensionais são usadas para mostrar que o paradoxo de Klein nunca aparece no caso do acoplamento vetorial não-mínimo, contrário ao que ocorre para um potencial vetorial minimamente acoplado. Um aparente paradoxo relacionado à localização de bósons na presença de potenciais fortes é resolvido através da introdução dos conceitos de massa efetiva e comprimento de onda Compton efetivo / The rst-order Du n-Kemmer-Petiau (DKP) formalism describes spin-0 and spin-1 particles and has been used to analyze relativistic interactions of hadrons with nuclei as an alternative to their conventional second-order Klein-Gordon and Proca counterparts. We present the general DKP equation, discuss conditions on the interactions which lead to a conserved current and e ects of parity, charge-conjugation and time-reversal transformations. Adopting a speci c representation for the DKP matrices, we set up the equations for the components of the DKP spinor in the presence of scalar and vector interactions. We point out that the space component of the nonminimal vector potential can not be absorbed into the spinor. We show that the space component of the nonminimal vector potential could be irrelevant for the formation of bound states for potentials vanishing at in nity but its presence is a sine qua non condition for con nement. Some aplications in unidimensional potentials are used to show that Klein's paradox never appears in the case of a nonminimal vector potential, contrary to what occurs for a minimally coupled vector potential. An apparent paradox related to the localization of bosons in the presence of strong potentials is solved by introducing the concepts of e ective mass and e ective Compton wavelength

nÃo hà / A saÃde do trabalhador no Brasil tomou novo rumo com uma nova visÃo, mais ampla e integral do processo saÃde-doenÃa, considerando-se as questÃes relacionadas a acidentes e doenÃas ocupacionais sobre o trabalho. Dentre as vÃrias doenÃas estÃo a Perda Auditiva Induzida pelo RuÃdo (PAIR) e os trabalhadores que sÃo continuamente expostos a compostos quÃmicos em ambientes industriais. Entre estes, figuram os chamados compostos hexavalentes e os compostos formados por cromo trivalente. O objetivo desta pesquisa foi verificar se a exposiÃÃo simultÃnea de ruÃdo e cromo potencializa o aparecimento da perda auditiva ocupacional dos trabalhadores de curtume em Teresina-PI. As caracterÃsticas da populaÃÃo em estudo, sÃo todos os trabalhadores do sexo masculino, divididos em 3 grupos, sendo: Grupo I - exposto a cromo e ruÃdo (n = 9); Grupo II - exposto a ruÃdo (n = 9); Grupo III - controle (n =10) na faixa etÃria de 38,11  5,9 , 30,83  7,4 e 27,40  7,0 anos, respectivamente. Os trabalhadores do Grupo I e II trabalham em mÃdia 9 horas diÃrias e 22,2% do grupo I apresentam problemas cardiovasculares e 16,7% do grupo II alteraÃÃo da pressÃo arterial. Em relaÃÃo ao tempo de trabalho, verifica-se um maior tempo de trabalho para os trabalhadores expostos a cromo e ruÃdo em mÃdia 13 anos, estes desenvolvem suas atividades laborais em sua maioria nos setores de curtimento, classificaÃÃo de peles e Ribeira, sÃo os que estÃo em contato permanente com o cromo (55%), enquanto que os expostos a ruÃdo (grupo II) sÃo os trabalhadores dos setores de acabamento, rebaixamento e lixadeira de couro (83,3%). Quando relacionado à funÃÃo e de acordo com a categoria profissional os que mais se expÃem a ruÃdo e cromo sÃo os auxiliares de produÃÃo, (44,5% exposto a ruÃdo e cromo e 91,5% expostos a ruÃdo). Em relaÃÃo aos EPIs somente (55,6%) de trabalhadores expostos ao cromo e ruÃdo utilizam protetor auricular do tipo plug; e nenhuma proteÃÃo para o cromo. Nos expostos somente a ruÃdo o uso de EPI à de apenas 25%. Sobre sua percepÃÃo quanto a sua prÃpria audiÃÃo, todos os grupos referem-na como boa, apenas 20% dos que responderam do grupo I referiu-se a sua audiÃÃo como ruim. No grupo exposto somente a ruÃdo 8,3% relatam otalgia, enquanto que 100% dos expostos a cromo e ruÃdo fazem esse relato, apresentando significÃncia p< 0,05. Os trabalhadores do Grupo I e II queixam-se de tonturas frequentes (44% e 25%), zumbido (22,2% e 50%) respectivamente. Quanto ao resultado do exame audiomÃtrico, 100% do Grupo Controle e os expostos a RuÃdo apresentaram Limiares Auditivos dentro dos PadrÃes de Normalidade enquanto 22,2% dos expostos a cromo e ruÃdo apresentaram perda auditiva neurossensorial. Quando avaliados os parÃmetros de cromo na urina, ocorreu um aumento significante no valor da dosagem de cromo dos trabalhadores expostos a cromo e ruÃdo p<0,001 (2,76  0,76 ) em relaÃÃo aos expostos somente a ruÃdo p<0,05 (1,62  1,77), quando comparados com o controle. Assim salienta-se a necessidade de investigaÃÃo da perda auditiva em trabalhadores de curtume como estratÃgia de prevenÃÃo, associados a contÃnuos programas educacionais relacionados ao uso correto de equipamentos de proteÃÃo individual tanto na exposiÃÃo a substÃncias quÃmicas como para ruÃdo.

When intense laser pulses interact with an atomic or solid target, high order harmonics of the fundamental laser frequency are generated. In the case of atoms, this highly nonlinear optical process is initiated by ionization and terminated by the energetic recollision and recombination of the ionized electron with its correlated ion. In this thesis I demonstrate, both theoretically and experimentally, that high harmonics from bulk crystals can originate from the recollision of electrons with their associated holes, similarly to the atomic case, but where ionization is replaced by excitation of electron-hole pairs that accelerate within the material. This model is first derived from a quantum-mechanical theory of the solid-laser interaction, and then confirmed experimentally in ZnO and Si crystals. Despite the link I establish between high harmonic generation in solids and gases, there are notable dissimilarities. These include: a generalized motion of electrons and holes in their respective bands and its consequences, a more prominent role of dephasing and enhanced sensitivity to perturbing fields. These aspects are investigated throughout this thesis. Finally, I develop a method that exploits the recollision mechanism to reconstruct the momentum-dependent band structure of solids.

The well-separated pair decomposition (WSPD) of the complete Euclidean graph defined on points in R 2 , introduced by Callahan and Kosaraju [JACM, 42 (1): 67-90, 1995], is a technique for partitioning the edges of the complete graph based on length into a linear number of sets. Among the many different applications of WSPDs, Callahan and Kosaraju proved that the sparse subgraph that results by selecting an arbitrary edge from each set (called WSPD-spanner) is a 1 + 8/(s − 4)-spanner, where s > 4 is the separation ratio used for partitioning the edges. Although competitive local-routing strategies exist for various spanners such as Yao-graphs, Θ-graphs, and variants of Delaunay graphs, few local-routing strategies are known for any WSPD-spanner. Our main contribution is a local-routing algorithm with a near-optimal competitive routing ratio of 1 + O(1/s) on a WSPD-spanner. Specifically, using Callahan and Kosaraju’s fair split-tree, we show how to build a WSPD-spanner with spanning ratio 1 + 4/s + 4/(s − 2) which is a slight improvement over 1 + 8/(s − 4). We then present a 2-local and a 1-local routing algorithm on this spanner with competitive routing ratios of 1 + 6/(s − 2) + 4/s and 1 + 8/(s − 2) + 4/s + 8/s 2 , respectively. Moreover, we prove that there exists a point set for which our WSPD-spanner has a spanning ratio of at least 1 + 8/s, thereby proving the near-optimality of its spanning ratio and the near-optimality of the routing ratio of both our routing algorithms.

Thesis advisor: Masayuki Wasa / Thesis advisor: Amir H. Hoveyda / This dissertation describes the development of cooperative catalyst systems for the regio- and enantio-selective α- and β-amino C-H functionalization of N-alkylamines, inspired by the concepts of frustrated Lewis pairs (FLPs). Prior to this dissertation research, the development of effective and broadly applicable catalytic protocol to transform amino C-H bonds with high enantioselectivity remained as a formidable problem. In Chapter 1, the recent advances in the field of amino C-H functionalization through hydride transfer process that served as intellectual foundations for this dissertation research is presented. As highlighted in the first chapter, key challenges of amino C-H functionalization are: (1) unreactive nature of α, β- and/or γ-amino C-H bonds, (2) requirement for the use of precious metal-based catalysts and external oxidants under acidic/basic and harsh conditions, (3) use of directing groups for regioselectivity, and (4) poor functional group tolerance. Inspired by the unique capability of FLPs to activate otherwise unreactive molecules while disfavoring undesirable acid-base complexation, we have developed a protocol for enantioselective α-amino C-H functionalization of N-alkylamines, where chiral and achiral Lewis acid catalysts work cooperatively (Chapter 2). The application of the cooperative catalyst system comprising of B(C6F5)3, a chiral Lewis acid, and a Brønsted base to the enantioselective β-amino C-H functionalization is described in Chapter 3. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

<p> Let t, k, v be three positive integers such that 2 ≤ t < k ≤ v. A Steiner system S(t, k, v) is a pair (V, B) where |V| = v and B is a collection of k-subsets of V, called blocks, such that every t-subset of V occurs in exactly one block in B. When t = 2, the Steiner system S(2, k, v) is sometimes called a Steiner 2-design.</p> <p> Given a Steiner 2-design, S = (V, B), with general block size k, a block-colouring of S is a mapping ¢ : B ---> C, where C is a set of colours. If |C| = n, then ¢ is an n-block-colouring. In this thesis we focus on block-colourings for Steiner 2-designs with k = 4 with some results for general block size k.</p> <p> In particular, we present known results for S(2, 4, v)s and the classical chromatic index. A classical block-colouring is a block-colouring in which any two blocks containing a common element have different colours. The smallest number of colours needed in a classical block-colouring of a design S = (V, B), denoted by x'(S), is the classical chromatic index.</p> <p> We also discuss n-block-colourings of type π, where π = ( π1, π2, ... , πs ) is a partition of the replication number r = v-1/k-1 for a Steiner system S(2,k,v). In particular, we focus on 8(2,4,v)s and the partitions (2, 1, 1, ... , 1), (3, 1, 1 ... , 1), and partitions of the form π = (π1, π2, ... , πs), where |πj -πil ≤ 1 for all 1 ≤ i < j ≤ s. These latter partitions are called equitable partitions and the corresponding block-colourings are called equitable block-colourings.</p> <p> Finally, we present results on the T-chromatic index for S(2, 4, v )s for various configurations T. The T-chromatic index for a Steiner system S(2, k, v), S, is the minimum number of colours needed to colour the blocks of S such that there are no monochromatic copies of T. In particular, we focus on configurations containing 2 lines and configurations containing 3 lines for both S(2, 4, v)s and general S(2, k, v)s. </p> / Thesis / Doctor of Philosophy (PhD)

The bulk structure and the nonpolar, stoichiometric (110) surface of stishovite, rutile structure type SiO₂, has been studied using a first principles, density functional method. The geometric and electronic structure, including the density of states, charge density, and electron localization function for both the bulk and the surface have been examined. The electron pair properties of both bulk and surface-layer atoms were found to be similar to molecular analogs. The analogs allowed for the description of surface electronic structure using simple molecular models. The adsorption of hydrogen fluoride was studied on the (110) surface. The geometry optimized and electronic structure have been found for various initial geometries. Relaxed structures of certain initial geometries give dissociated hydrogen fluoride upon geometry optimization. / Master of Science