Global ETD Search

21	Measuring broadband, ultraweak, ultrashort pulses Shreenath, Aparna Prasad 14 July 2005 (has links) Many essential processes and interactions on atomic and molecular scales occur at ultrafast timescales. The ability to measure and manipulate ultrashort pulses hold the key to probing and understanding these key processes that physicists, engineers, chemists and biologists study today. Measuring ultrashort pulses means that we measure both the intensity (which is a function of time) and the phase of the pulse in time. Or alternately we might measure spectrum and spectral phase (in the corresponding Fourier domain). In the early 1990's, the invention of FROG opened up the field of ultrashort measurement with it's ability to measure the complete pulse. Since then, there have been a whole host of pulse measurement techniques that have been invented to measure all sorts of ultrashort pulses. However, no variation of FROG nor any other fs pulse measurement technique, for that matter, has yet been able to completely measure arbitrary ultraweak femtosecond light pulses such as those found in nature. In this thesis, we will explore a couple of highly sensitive methods in a quest to measure ultraweak ultrashort pulses. We explore the use of Spectral Interferometry, a known sensitive technique as one possibility. We find that it has certain drawbacks that make it not necessarily suitable to tackle this problem. But in the course of our quest, we find that this technique is highly suitable for measuring 10s of picosecond-long shaped pulses. We discuss a couple of developments which make SI highly practical to use for such shaped pulse-measurements. We also develop a new technique which is a variation of FROG, based on the non-linearity of Difference Frequency Generation and Optical Parametric Amplification, which can amplify pulses as weak as a few hundred attojoules to be able to spectrally resolve them and measure the full intensity and phase of these pulses. This technique offers great potential to measure generalized ultraweak ultrashort pulses. Spectral interferometry Direction-of-time ambiguity NOPA XFROG POLKADOT FROG OPA XFROG Dual quadrature spectral interferometry Pulse techniques (Electronics) Laser pulses, Ultrashort Measurement Picosecond pulses Measurement
22	Using functionalized gold nanoparticles to determinate environmental samples and biomolecules Lai, Yi-Jhen 22 June 2011 (has links) ¤@¡BRole of 5-thio-(2-nitrobenzoic acid)-capped gold nanoparticles in the sensing of chromium(VI): remover and sensor This study describes a simple, rapid method for sensing Cr(VI) using 5-thio-(2-nitrobenzoic acid) modified gold nanoparticles (TNBA-AuNPs) as a remover for Cr(III) and as a sensor for Cr(VI). We discovered that TNBA-AuNPs were dispersed in the presence of Cr(VI), whereas Cr(III) induced the aggregation of TNBA-AuNPs. Due to this phenomenon, TNBA-AuNPs can be used as a sorbent material for the removal of > 90% Cr(III), without removing Cr(VI). After centrifuging a solution containing Cr(III), Cr(VI), and TNBA-AuNPs, Cr(III) and Cr(VI) were separately present in the precipitate and supernatant. In other words, TNBA-AuNPs are capable of separating a mixture of Cr(III) and Cr(VI). The addition of ascorbic acid to the supernatant resulted in a reduction of Cr(VI) to Cr(III), driving the aggregation of TNBA-AuNPs. The selectivity of this approach is more than 1000-fold for Cr(VI) over other metal ions. The minimum detectable concentration of Cr(VI) was 1 £gM using this approach. Inductively coupled plasma mass spectrometry provided an alternative for the quantification of Cr(III) and Cr(VI) after a mixture of Cr(III) and Cr(VI) had been separated by TNBA-AuNPs. The applicability of this approach was validated through the analysis of Cr(VI) in drinking and tap water. ¤G¡BFluorescent Sensing of Total, Protein-bound, Free, and Oxidized Homocysteine in Plasma through the Combination of Tris(2-carboxyethyl)Phosphine Reduction, Fluorosurfactant-Capped Gold Nanoparticles Extraction, and o-Phthaldialdehyde Derivatization This study reports a simple, selective, and sensitive method for fluorescent detection of total, protein-bound, free, and oxidized homocysteine (HCys) using tris(2-carboxyethyl)phosphine (TCEP) as a reducing agent, fluorosurfactant-capped gold nanoparticles (FSN-AuNP) as a preconcentrating probe, and o-Phthaldialdehyde (OPA) as a derivatizing agent. TCEP was used to reduce the disulfide bonds of protein-bound and oxidized HCys. FSN-AuNPs were capable of extracting HCys from a complicated complex because the FSN capping layer can stabilize the AuNPs in a high-salt solution and inhibit non-specific adsorption. HCys was selectively derivatized with OPA in the absence of a nucleophile. By taking advantage of these features, the selectivity of the proposed system is greater than 100-fold for HCys and homocystine (HCys-HCys disulfide; diHCys) compared to any aminothiols. The limits of detection (LODs) for HCys and diHCys were 4.4 and 4.6 nM, respectively. Compared to other sensors, the proposed system provides an approximately 3-300-fold improvement in the detection of HCys. Different forms of plasma HCys were determined by varying the order of disulfide reduction with TCEP. The proposed system was successfully applied to determine the total, protein-bound, free, and oxidized HCys in plasma. To the best of our knowledge, the proposed system not only provides the first method for detecting various forms of plasma HCys, but also has the lowest LOD value for HCys when compared to other sensors. o-Phthaldialdehyde (OPA) homocysteine(HCys) homocystine(diHcys) FSN-AuNPs Tris¡]2-carboxyethyl¡^phosphine (TCEP) 5-thio-(2-nitrobenzoic acid) (TNBA) K2Cr2O7 CrCl3 gold nanoparticles (AuNPs) ascorbic acid
23	Pass-by noise contribution analysis of electric vehicles Falk Lissel, Linus January 2014 (has links) In the modern urban lifestyle, more and more people are exposed to noise pollution in form of traffic noise. As a response to this, the automotive OEMs (Original Equipment Manufacturer) are put under pressure to reduce the emitted noise from vehicles. To be able to meet the upcoming, stricter regulations, the automotive OEMs seeks new techniques to be able to front load the pass-by noise engineering in the vehicle development process and to identify and understand the different sources that contributes to the exterior noise.Earlier exterior sources ranking using ASQ (Airborn Source Quantification) with an energetic approach during pass-by noise test has yielded very good and reliable results for an ICE (Internal Combustion Engine) vehicle.In this Master Thesis, two exterior source ranking methods have been tested and evaluated for an electric vehicle during in-room pass-by noise test. The two methods were: ASQ and OPA (Operational Path Analysis). In total, five models were built from the two methods and each model was evaluated for, in total, three driving conditions corresponding to the current ISO362-1:2007 and the proposed, revised version.The results show that the ASQ models are not capable to correctly estimate the engine contribution due to its high tonality. Moreover, it was seen that the energetic ASQ model is very sensitive to small changes. Both ASQ models underestimated the tire noise.The OPA model on the other hand managed to estimate the total contribution very well. Both the engine contribution and the tire contributions are well estimated. Nevertheless, OPA as method has several weaknesses and building an OPA model is not a straightforward task. Its weaknesses and the process to reach a final OPA model are discussed in this thesis.It was seen that one of the most crucial steps in an OPA model is to have clean references to get meaningful results. A MIMO-FIR filter was therefore used to filter out engine harmonics from the tire references. Its principles and importance for the end results are also discussed.Included is also an overview of the basic principles in TPA (Transfer Path Analysis), ASQ, OPA and in room pass by noise test as well as a description of the test campaign. Transfer Path Analysis (TPA) Airborn Source Quantification (ASQ) Operational Path Analysis (OPA) Time domain In-room Pass-By Noise test MIMO FIR-filter Engineering and Technology Teknik och teknologier
24	Les engagements contractuels des actionnaires de référence lors de l'introduction en bourse / Contractual commitments from the main shareholders at the initial public offering stage Ducros, Éric 13 March 2009 (has links) Ce travail vise à déterminer dans le cadre des sociétés s’introduisant en bourse les facteurs explicatifs de la présence d’engagements contractuels par les principaux actionnaires d’une part et leur impact sur la valeur de la firme d’autre part. Le terme « engagement contractuel » fait référence à deux mécanismes mis en place au moment de l’introduction en bourse : les engagements de conservation d’actions par les dirigeants et les pactes d’actionnaires. Notre étude porte sur un échantillon de 292 entreprises introduites en bourse entre 1996 et 2000 sur le nouveau marché et le second marché de la bourse de Paris. Nos résultats montrent que la présence et la durée des engagements de conservation d’actions des dirigeants servent à signaler la valeur de la firme lorsque l’asymétrie d’information est grande mais aussi à compenser certaines inefficiences du système de gouvernance de l’entreprise. Nous observons également un impact négatif sur la valeur de la firme des engagements de conservation des dirigeants alors que ceux concernant les sociétés de capital risque l’influence positivement. Concernant les pactes d’actionnaires, nos travaux montrent que leur mise en place est d’autant plus probable que les dirigeants anticipent une cession future de l’entreprise. Ils ont par ailleurs une influence positive sur la valeur de la firme tant qu’ils ne protègent pas les signataires d’une prise de contrôle hostile ; dans ce dernier cas l’effet sur la valeur de la firme est négatif. Finalement, nous montrons qu’il existe une réaction négative du cours de bourse autour du jour de l’expiration des engagements de conservation. / Using a sample of IPO firms, we try to figure out what are the factors influencing the adoption of lockups and shareholder agreements and we also try to assess the impact on firm value of these two commitments. Our study is based on a sample of 292 IPOs made between 1996 and 2000 on the French nouveau marché and second marché. We found that the adoption of lockups and their length may serve to alleviate information asymmetry at the IPO time. Our results also give pieces of evidence that this mechanism may compensate for some inefficiencies of the corporate governance setting. We found that lockups undertaken by managers have a negative effect on firm value whereas lockups by venture capital firms have a positive one. With regards to shareholder agreements, our tests show that the probability of adopting such a commitment is positively related to managers’ anticipation of a future sale of the firm. We also found that shareholder agreements have a positive effect on firm value as long as they do not insulate the company from the threat of a hostile takeover. In this latter case, the effect on firm value is negative. Finally, we found a negative return around the day where lockups are released. Actionnariat des dirigeants Asymétrie d'information Engagements de conservation Fusion-acquisitions Gouvernance Introduction en bourse Q de Tobin OPA amicales OPA hostiles Pactes d'actionnaires Valeur de la firme Corporate governance Firm value Friendly takeovers Hostile takeovers Information asymmetry IPO Lockups Managers' shareholdings Mergers and acquisitions Shareholder agreements Tobin's Q Venture capital's shareholdings
25	Oferta pública de aquisição de ações por alienação de controle de companhias abertas brasileiras Tourinho, Marcelo Abreu dos Santos 14 June 2012 (has links) Made available in DSpace on 2016-04-26T20:21:02Z (GMT). No. of bitstreams: 1 Marcelo Abreu dos Santos Tourinho.pdf: 1153194 bytes, checksum: f5a573ee7c27d41958b5c0071bcddbb1 (MD5) Previous issue date: 2012-06-14 / This work aims to analyze and explore the controversial aspects related to mandatory bid rule under Brazilian Corporate Law (Law 6,404/76), which extends to voting minority shareholders the right to sell their shares in case of a control transfer. For this purpose we analyze (i) the nature of control , as a power to direct the corporation s business; (ii) the legal definition of controlling shareholder under Brazilian law; (iii) the history of the Brazilian institutional framework; (iv) the different justifications for the rule under Brazilian and foreign doctrines; (v) the elements for the characterization of the transfer of control, taking into consideration the key precedents of Comissão de Valores Mobliários - CVM; and (vi) the mandatory bid rule procedures / O presente trabalho tem por objetivo analisar e explorar os aspectos controversos envolvendo a regra da oferta pública de aquisição de ações prevista no art. 254-A da Lei 6.404/76, que estende aos minoritários titulares de ações votantes o direito de alienar suas ações em casos de alienação de controle. Para tal analisamos (i) a natureza do controle , entendido como poder de direcionar a atividade empresarial; (ii) a definição legal de acionista controlador de acordo com a legislação brasileira; (iii) o histórico do instituto; (iv) as diferentes justificativas para o instituto, segundo as doutrinas brasileira e estrangeiras; (v) os elementos para a caracterização da alienação de controle, abordando os principais precedentes da Comissão de Valores Mobiliários CVM; e (vi) o procedimento para a realização de uma oferta pública Alienação de controle OPA Poder de controle CVM Acionistas Aquisição de controle Proteção dos minoritários Transfer of control Mandatory bid rule Tender offer Power of control Shareholder Acquisition of control Minority protection
26	Gerenciamento de resultados em fechamento de capital Santos, Isabela Travaglia 15 March 2010 (has links) Mercados financeiros e finanças corporativas / Submitted by Cristiane Shirayama (cristiane.shirayama@fgv.br) on 2011-05-21T20:09:53Z No. of bitstreams: 1 61080100021.pdf: 1579434 bytes, checksum: 48ff2e28230b8ab64ed6919d82c68a84 (MD5) / Approved for entry into archive by Gisele Isaura Hannickel(gisele.hannickel@fgv.br) on 2011-05-23T11:37:23Z (GMT) No. of bitstreams: 1 61080100021.pdf: 1579434 bytes, checksum: 48ff2e28230b8ab64ed6919d82c68a84 (MD5) / Approved for entry into archive by Gisele Isaura Hannickel(gisele.hannickel@fgv.br) on 2011-05-23T11:39:50Z (GMT) No. of bitstreams: 1 61080100021.pdf: 1579434 bytes, checksum: 48ff2e28230b8ab64ed6919d82c68a84 (MD5) / Made available in DSpace on 2011-05-23T12:18:05Z (GMT). No. of bitstreams: 1 61080100021.pdf: 1579434 bytes, checksum: 48ff2e28230b8ab64ed6919d82c68a84 (MD5) Previous issue date: 2010-03-15 / This study investigates the dynamics of earnings management of Brazilian companies previously to their going private operations in the period of 1999 from 2009. Three main issues are investigated: the type of operation (LBO or Acquisition), the periods in which occur significant manipulation and the legislation change in 2001, which main goal was to cohibit the abusive rebuying of shares by the companies that wanted to go private prior to the going-private operation. The sample is composed of 132 companies that went private from 1999 to 2009 and the data were quarterly collected ranging five years. We found evidence that the sample firms manipulated their earnings approximately two years before going private. Also, some results show that there are differences in the direction of earnings management depending on the type of public-to-private operation: LBOs firms tended to manage their earnings up, as well as the companies that were acquired by their controlling firms, while the other acquisitions showed signs of downward manipulations. Finally, we found evidence that the legislation change in 2001 not only might have changed the pattern of firm´s manipulation but has also increased earnings management right after its effective date. / Esse trabalho investiga a dinâmica da manipulação de resultados de empresas brasileiras que fecharam o capital no período de 1999 a 2009. Dentre os fatores investigados estão o tipo de fechamento (OPA, aquisição, aquisição por controladoras), o período de manipulação e a mudança que a Lei nº 10.303/2001 (cujo objetivo era coibir o fechamento branco de capital) teria sobre o gerenciamento. A amostra utilizada é composta de 132 empresas que realizaram o fechamento no período citado, sendo o ciclo de dados coletado para cada empresa de vinte trimestres. Foram achados indícios de que essas empresas manipularam seus ganhos aproximadamente dois anos antes de seu fechamento. Além disso, foram encontradas evidências de diferença de direção de manipulação para os tipos de fechamento: empresas cujos fechamentos ocorreram através de OPA, assim como as que sofreram aquisição por suas controladoras, tenderiam a manipular seus ganhos para baixo, enquanto que as demais aquisições se caracterizariam por terem seus resultados adulterados para cima. Por fim, foram achados indícios de que a Lei nº 10.303/2001 tenha alterado o comportamento de manipulação contábil das empresas e de que houve um aumento de manipulação logo em seguida à sua vigência. Fechamento de capital Manipulação contábil Gerenciamento de resultados Oferta pública de ações (OPA) Aquisição Acumulações discricionárias correntes Public-to-private Going private Earnings management Leverage buyout (LBO) Acquisition Discretionary current accruals Administração de empresas Sociedades por ações - Brasil Sociedades por ações - Avaliação Sociedades comerciais - Finanças
27	Les moyens de défense contre les OPA hostiles / Antitakeover defenses Maouche, Samia 27 November 2017 (has links) Opérations particulièrement complexes, les offres publiques d'acquisition ne cessent de faire parler d'elles, plus particulièrement lorsqu'elles présentent un caractère hostile pour la société visée. De nombreux efforts législatifs ont été mis en œuvre en vue d'encadrer les OPA et de lutter contre les prises de contrôle rampantes. L'analyse du droit positif permet de mettre en lumière ces différents efforts ainsi que leur mise en œuvre à travers diverses techniques par les sociétés visées. Ces dernières ont par ailleurs développé un certain nombre de mécanismes de défense anti-OPA particulièrement efficaces, mais se révélant le plus souvent insuffisants face à l'ingéniosité dont peut faire preuve l'initiateur. Le droit positif montre ainsi ses limites face à des pratiques qui ne cessent d'évoluer. L'analyse prospective du droit anti-OPA permet d'observer les nouvelles mutations que subit le droit positif au regard des nouveaux enjeux économiques. Elle permet également d'envisager de nouveaux modes d'appréhension des OPA hostiles. Il est ainsi possible d'observer que le gouvernement d'entreprise prend une place considérable dans la vie des sociétés cotées. De même, la montée en puissance de la régulation et l'interventionnisme de l’État sont de plus en plus marqués ; et les salariés s'impliquent de plus en plus dans la gestion de l'entreprise. L'ensemble de ces paramètres marquent un glissement progressif vers une réorganisation du mode de fonctionnement des sociétés, ce qui a amené au développement du soft law, un droit à la frontière du droit positif et des pratiques des sociétés. Le soft law constitue à ce titre une approche inédite des OPA hostiles, dont l'analyse permet de cerner les apports liés à la mutation du droit positif et d'envisager l'émergence de nouveaux moyens de défense. Celui-ci doit toutefois demeurer complémentaire au cadre législatif et réglementaire existant. / No abstract Prise de contrôle Offres publiques d'achat Prise de contrôle hostile Offre obligatoire Offre amicale Sociétés cotées Moyens de défense Actions Initiateur Société cible Franchissement de seuils Autorité des marchés financiers (AMF) Actionnaires Droits de vote Action de concert Salariés Conseil d'administration Comité d'entreprise Augmentation de capital Transparence Chevalier blanc Bons bretons (pilules empoisonnées) Droit souple Gouvernement d'entreprise Contre-OPA Sanctions Takeover bid Hostile takeover bid Mandatory bid Amicable bid Listed companies Antitakeover defenses Shares Raider Target company Crossing of shareholding thresholds Amf Shareholders Voting rights Concert Employees Board of directors Works council Increase of capital Transparency Wight knight Poison pills Soft law Corporate governance Pacman Sanctions 330
28	Constructing and Commissioning HELIOS – A High Harmonic Generation Source for Pump-Probe Measurements with sub 50 fs Temporal Resolution : The Development of Experimental Equipment for Extreme Ultraviolet Spectroscopy Terschlüsen, Joachim A. January 2016 (has links) This thesis presents HELIOS, an in-house laboratory for time-resolved pump-probe spectroscopy with extreme-ultraviolet (XUV) probe radiation. A wide span of pump wavelengths can be generated using commercial laser equipment while XUV probe radiation is generated via a high harmonic generation process in a noble gas delivering probe photons with energies between 20 eV and 72 eV. The XUV beam path features a time-preserving monochromator and was constructed and built in-house. HELIOS features an overall time resolution of about 50 fs when using 800 nm pump and 41 eV probe photons. An energy resolution of 110 meV at 41 eV photon energy can be achieved. HELIOS features two beamlines. One µ-focus beamline with an XUV focal size of about 20 µm can be used with experiments that require such a small XUV focal size as well as with different end stations. The other beamline features a semi-permanently mounted end station for angle-resolved photoelectron spectroscopy under ultra-high vacuum conditions. Experiments demonstrating the usability of HELIOS and the two beamlines are presented. A pump-probe measurement on graphene demonstrates the capability of determining a large part of the k-space in only one measurement due to the use of an ARTOF angle-resolved time-of-flight electron spectrometer. A non-angle-resolved pump-probe measurement on the conducting polymer PCPDTBT demonstrates the high signal-to-noise ratio achievable at this beamline in non-angle-resolved photoelectron-spectroscopy pump-probe measurements. The usability of the µ-focus beamline is demonstrated with time-resolved measurements on magnetic samples employing an in-house-designed spectrometer. These experiments allow the retrieval of element-specific information on the magnetization within a sample employing the transversal magneto-optical Kerr effect (T-MOKE). Additionally, a Fourier transform spectrometer for the XUV is presented, the concept was tested at a synchrotron and it was used to determine the longitudinal coherence of the XUV radiation at HELIOS. Angle-resolved time-of-flight Angle resolved time of flight ARTOF ARPES tr-ARPES fs fs resolution Fourier transform spectrometer Fourier-transform spectrometer Fourier transform spectroscopy Fourier-transform spectroscopy FTS gas cell high harmonic generation laser liquid jet monochromator HELIOS HHG off-plane mount off plane mount OPA optical parametric amplifier PCPDTBT pulse shaping pump probe pump-probe measurements pump-probe measurements pump-probe spectroscopy pump-probe spectroscopy Rowland spectrometer time-of-flight spectrometer time of flight spectrometer TOF time-resolved spectroscopy time resolved spectroscopy time-resolved experiments time resolved experiments T-MOKE tr-PES PES photoelectron spectroscopy transverse magneto optical Kerr effect transverse magneto-optical Kerr effect ultrafast ultra-high vacuum ultra high vacuum UHV XUV VUV X-rays Permalloy magnetization dynamic
29	Le droit français des OPA - un modèle pour le droit brésilien ? / The French law of takeover bids, a model for the brazilian law ? Mendia Twardowsky, Bianca 29 November 2017 (has links) L'objectif de cette thèse est d'analyser le système juridique français et brésilien concernant les stratégies de défense contre les offres publiques d'acquisition visant à prendre le contrôle des sociétés cotées en bourse. Les offres publiques d'acquisition font l'objet d'un vif débat, plus particulièrement lorsqu'elles présentent un caractère hostile pour la société cible. En France, de nombreux efforts législatifs ont été mis en œuvre en vue d'encadrer les OPA et de lutter contre les prises de contrôle rampantes. L'analyse du droit positif permet de mettre en lumière ces différents efforts ainsi que leur mise en œuvre à travers diverses techniques par les sociétés visées. Grâce à l'analyse juridique des stratégies anti-OPA en France, le système brésilien peut prendre connaissance de cette expérience et trouver la meilleure approche juridique pour les sociétés cotées ayant un capital flottant important. Au Brésil, la récente vague d'IPO a été possible grâce à la réforme dans la bourse BM&FBOVESPA. Dorénavant, la BM&FBOVESPA présente le scénario idéal pour prendre le contrôle des sociétés cotées. Ainsi, l'importance de ce thème est le résultat de la dispersion de l'actionnariat après la première vague d'introduction en bourse dans le marché de capitaux brésilien, et en France, elle se traduit par l'évolution dans environnement légal des défenses anti-OPA face à des pratiques qui ne cessent d'évoluer. / The objective of this thesis is to analyse the French experience and the Brazilian legal environment concerning the defense strategies against hostile corporate takeovers aimed at taking control over public companies. Through the analysis of the French legal system of the anti-takeover strategies, the Brazilian system will be able to acquire this experience and find the best legal approach for Brazilian public companies with dispersed ownership. The importance of this theme is the result of the ownership dispersion following the first IPOs in the current Brazilian securities exchange market, which provides the ideal scenario for taking control of these publicly-traded companies, as well as the changes and the evolution in the French legal environment. Prise de contrôle Offre publique d'acquisition Prise de contrôle hostile Offre obligatoire Offre amicale Sociétés cotées Stratégie de défense anti-OPA Sanctions Actions Société cible Raider Franchissement de seuils Autorité des marchés financiers (AMF) Cvm Cade Bm&fbovespa Nivel 1 Nivel 2 Novo mercado Ipo Capital flottant Actionnaires Droits de vote Action de concert Salariés Conseil d'administration Comité d'entreprise Augmentation de capital Transparence Chevalier blanc Bons bretons Poison pill Gouvernement d'entreprise Takeover bid Hostile takeover bid Ownership dispersion Securities exchange commission Mandatory bid Listed companies Anti-takeover defenses Sanctions Shares Raider Target company Amf Cvm Cade Bm&fbovespa Nivel 1 Nivel 2 Novo mercado Initial public offering Free float Shareholders Voting rights Board of directors Transparency White knight Poison pills Corporate governance 346.44

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