<p>This doctoral thesis summarizes research in quantum cryptography done at the Department of Electronics and Telecommunications at the Norwegian University of Science and Technology (NTNU) from 1998 through 2007.</p><p>The opening parts contain a brief introduction into quantum cryptography as well as an overview of all existing single photon detection techniques for visible and near infrared light. Then, our implementation of a fiber optic quantum key distribution (QKD) system is described. We employ a one-way phase coding scheme with a 1310 nm attenuated laser source and a polarization-maintaining Mach-Zehnder interferometer. A feature of our scheme is that it tracks phase drift in the interferometer at the single photon level instead of employing hardware phase control measures. An optimal phase tracking algorithm has been developed, implemented and tested. Phase tracking accuracy of +-10 degrees is achieved when approximately 200 photon counts are collected in each cycle of adjustment. Another feature of our QKD system is that it uses a single photon detector based on a germanium avalanche photodiode gated at 20 MHz. To make possible this relatively high gating rate, we have developed, implemented and tested an afterpulse blocking technique, when a number of gating pulses is blocked after each registered avalanche. This technique allows to increase the key generation rate nearly proportionally to the increase of the gating rate. QKD has been demonstrated in the laboratory setting with only a very limited success: by the time of the thesis completion we had malfunctioning components in the setup, and the quantum bit error rate remained unstable with its lowest registered value of about 4%.</p><p>More than half of the thesis is devoted to various security aspects of QKD. We have studied several attacks that exploit component imperfections and loopholes in optical schemes. In a large pulse attack, settings of modulators inside Alice's and Bob's setups are read out by external interrogating light pulses, without interacting with quantum states and without raising security alarms. An external measurement of phase shift at Alice's phase modulator in our setup has been demonstrated experimentally. In a faked states attack, Eve intercepts Alice's qubits and then utilizes various optical imperfections in Bob's scheme to construct and resend light pulses in such a way that Bob does not distinguish his detection results from normal, whereas they give Bob the basis and bit value chosen at Eve's discretion. Construction of such faked states using several different imperfections is discussed. Also, we sketch a practical workflow of breaking into a running quantum cryptolink for the two abovementioned classes of attacks. A special attention is paid to a common imperfection when sensitivity of Bob's two detectors relative to one another can be controlled by Eve via an external parameter, for example via the timing of the incoming pulse. This imperfection is illustrated by measurements on two different single photon detectors. Quantitative results for a faked states attack on the Bennett-Brassard 1984 (BB84) and the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocols using this imperfection are obtained. It is shown how faked states can in principle be constructed for quantum cryptosystems that use a phase-time encoding, the differential phase shift keying (DPSK) and the Ekert protocols. Furthermore we have attempted to integrate this imperfection of detectors into the general security proof for the BB84 protocol. For all attacks, their applicability to and implications for various known QKD schemes are considered, and countermeasures against the attacks are proposed.</p><p>The thesis incorporates published papers [J. Mod. Opt. 48, 2023 (2001)], [Appl. Opt. 43, 4385 (2004)], [J. Mod. Opt. 52, 691 (2005)], [Phys. Rev. A 74, 022313 (2006)], and [quant-ph/0702262].</p>

This doctoral thesis summarizes research in quantum cryptography done at the Department of Electronics and Telecommunications at the Norwegian University of Science and Technology (NTNU) from 1998 through 2007. The opening parts contain a brief introduction into quantum cryptography as well as an overview of all existing single photon detection techniques for visible and near infrared light. Then, our implementation of a fiber optic quantum key distribution (QKD) system is described. We employ a one-way phase coding scheme with a 1310 nm attenuated laser source and a polarization-maintaining Mach-Zehnder interferometer. A feature of our scheme is that it tracks phase drift in the interferometer at the single photon level instead of employing hardware phase control measures. An optimal phase tracking algorithm has been developed, implemented and tested. Phase tracking accuracy of +-10 degrees is achieved when approximately 200 photon counts are collected in each cycle of adjustment. Another feature of our QKD system is that it uses a single photon detector based on a germanium avalanche photodiode gated at 20 MHz. To make possible this relatively high gating rate, we have developed, implemented and tested an afterpulse blocking technique, when a number of gating pulses is blocked after each registered avalanche. This technique allows to increase the key generation rate nearly proportionally to the increase of the gating rate. QKD has been demonstrated in the laboratory setting with only a very limited success: by the time of the thesis completion we had malfunctioning components in the setup, and the quantum bit error rate remained unstable with its lowest registered value of about 4%. More than half of the thesis is devoted to various security aspects of QKD. We have studied several attacks that exploit component imperfections and loopholes in optical schemes. In a large pulse attack, settings of modulators inside Alice's and Bob's setups are read out by external interrogating light pulses, without interacting with quantum states and without raising security alarms. An external measurement of phase shift at Alice's phase modulator in our setup has been demonstrated experimentally. In a faked states attack, Eve intercepts Alice's qubits and then utilizes various optical imperfections in Bob's scheme to construct and resend light pulses in such a way that Bob does not distinguish his detection results from normal, whereas they give Bob the basis and bit value chosen at Eve's discretion. Construction of such faked states using several different imperfections is discussed. Also, we sketch a practical workflow of breaking into a running quantum cryptolink for the two abovementioned classes of attacks. A special attention is paid to a common imperfection when sensitivity of Bob's two detectors relative to one another can be controlled by Eve via an external parameter, for example via the timing of the incoming pulse. This imperfection is illustrated by measurements on two different single photon detectors. Quantitative results for a faked states attack on the Bennett-Brassard 1984 (BB84) and the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocols using this imperfection are obtained. It is shown how faked states can in principle be constructed for quantum cryptosystems that use a phase-time encoding, the differential phase shift keying (DPSK) and the Ekert protocols. Furthermore we have attempted to integrate this imperfection of detectors into the general security proof for the BB84 protocol. For all attacks, their applicability to and implications for various known QKD schemes are considered, and countermeasures against the attacks are proposed. The thesis incorporates published papers [J. Mod. Opt. 48, 2023 (2001)], [Appl. Opt. 43, 4385 (2004)], [J. Mod. Opt. 52, 691 (2005)], [Phys. Rev. A 74, 022313 (2006)], and [quant-ph/0702262].

Campylobacter jejuni is the leading bacterial cause of gastrointestinal diarrheal disease in humans worldwide. This zoonotic pathogen has a complex epidemiology due to its presence in many different host organisms. The overall aim of this thesis was to explore the role of amoebae of the genus Acanthamoeba as an intermediate host and vector for survival and dissemination of C. jejuni. Earlier studies have shown that C. jejuni can enter, survive and replicate within Acanthamoebae spp. In this thesis, I have shown that C. jejuni actively invades Acanthamoeba polyphaga. Once inside, C. jejuni could survive within the amoebae by avoiding localization to degradative lysosomes. We also found that A. polyphaga could protect C. jejuni in acid environments with pH levels far below the range in which the bacterium normally survives. Furthermore, low pH triggered C. jejuni motility and invasion of A. polyphaga. In an applied study I found that A. polyphaga also could increase the survival of C. jejuni in milk and juice both at room temperature and at +4ºC, but not during heating to recommended pasteurization temperatures. In the last study we found that forty environmental C. jejuni isolates with low bacterial concentrations could be successfully enriched using the Acanthamoeba-Campylobacter coculture (ACC) method. Molecular genetic analysis using multilocus sequence typing (MLST) and sequencing of the flaA gene, showed no genetic changes during coculture. The results of this thesis have increased our knowledge on the mechanisms behind C. jejuni invasion and intracellular survival in amoebae of the genus Acanthamoeba. By protecting C. jejuni from acid environments, Acanthamoebae could serve as important reservoirs for C. jejuni e.g. during acid sanitation of chicken stables and possibly as vectors during passage through the stomach of host animals. Furthermore, Acanthamoeba spp. could serve as a vehicle and reservoir introducing and protecting C. jejuni in beverages such as milk and juice. Validation of the ACC method suggests that it is robust and could be used even in outbreak investigations where genetic fingerprints are compared between isolates. In conclusion, Acanthamoeba spp. are good candidates for being natural hosts and vectors of C. jejuni.

La multiplication des résistances aux antibiothérapies actuelles et l’utilisation potentielle de bactéries pathogènes dans le cadre d’attentats bioterroristes rendent nécessaire la recherche de nouvelles cibles biologiques et la découverte de nouvelles stratégies antibiotiques. Dans ce contexte, les mécanismes d’assimilation du fer chez les bactéries à Gram négatif sont des cibles particulièrement prometteuses. Le fer est en effet un élément essentiel à la vie, mais peu biodisponible. Les bactéries ont donc développé des mécanismes efficaces pour subvenir à leurs besoins en fer. Ces mécanismes de transport nécessitent un apport d’énergie fourni par une machinerie bactérienne complexe, la machinerie TonB. La protéine TonB, qui joue un rôle central dans le fonctionnement de cette machinerie, est la cible de notre approche. Nous souhaitons séquestrer cette protéine dans le périplasme grâce à des composés peptidiques fonctionnalisés par des hétérocycles de type isoindole ou 1,2,4-triazine. La conception et la synthèse de ces molécules sont présentées dans ce manuscrit, ainsi que leurs perspectives de vectorisation en utilisant une stratégie dite du "cheval de Troie". Notre contribution à la mise au point d’un test d’affinité in vitro est également abordée. / The increasing resistances to the current antibiotherapies, and the potential use of pathogenic bacteria as biological weapons led us to the absolute necessity of discovering new biological targets and new antibiotic strategies. In this context, iron uptake pathways of Gram negative bacteria are promising targets. Indeed, iron is an essential nutrient, but it has a low bioavailability. Bacteria have developed efficient iron uptake pathways in order to proliferate. Iron is transported in the bacterial cell by specific outer membrane transporters and thanks to the energy provided by a complex molecular machinery, called TonB. The TonB protein, which is the keystone of this machinery, is a key target for the development of new antibiotics. We would like to sequester this protein in the periplasm thanks to molecules constituted of a peptidic moiety and a heterocyclic moiety such as isoindole or 1,2,4-triazine. The conception and the synthesis of these compounds are presented in this document, as well as their possibilities to be vectorized using a “Trojan Horse” strategy. Our contribution to the development of an in vitro test of affinity is presented as well.

[ES] El espectro de la luz solar está compuesto por una amplia gama de radiaciones electromagnéticas las cuales tienen diferentes impactos sobre la vida en la tierra. Entre ellas, las pertenecientes a la región ultravioleta toman un papel principal cuando nos referimos a la fotobiología, ya que pueden interactuar con las biomoléculas por medio de procesos tanto directos como fotosensibilizados. Como resultado, estas biomoléculas pueden sufrir modificaciones que no siempre tienen efectos beneficiosos. En este contexto, los daños fotoinducidos al ADN son de gran relevancia ya que están estrechamente relacionados con la creciente incidencia de cáncer de piel. Por ello, es necesario investigar tanto los mecanismos involucrados en dichos procesos como el desarrollo de nuevas estrategias para combatirlos. En la presente tesis se da respuesta a estas necesidades mediante el desarrollo y empleo de grupos protectores fotolábiles (PPG). En una primera parte se avanza en el desarrollo de nuevos PPG basados en filtros solares. Estos ofrecen la ventaja de actuar, una vez liberados, como un escudo protector frente a la radiación ultravioleta. En este contexto, en el Capítulo 3 se profundiza en las propiedades fotofísicas y fotoquímicas de los sistemas formados por la avobenzona como PPG de ácidos carboxílicos, más concretamente del ketoprofeno (KP) y del naproxeno (NPX). En este estudio se analiza por medio de modelado molecular y técnicas espectroscópicas la influencia que tiene la energía relativa del triplete de la avobenzona en su forma dicetónica, 3AB(K)*, respecto a la de los compuestos protegidos en el proceso de liberación. Siguiendo en esta misma línea de trabajo, en el Capítulo 4 se ha desarrollado un nuevo PPG capaz de liberar el filtro solar oxibenzona (OB) junto con compuestos carbonílicos. En una segunda parte, el foco de atención se ha puesto en el concepto de "Caballo de Troya", el cual establece que ciertas lesiones del ADN pueden actuar a su vez como fotosensibilizadores endógenos generando así nuevas lesiones en su entorno. En este contexto, en el Capítulo 5 se han estudiado, mediante métodos tanto experimentales como teóricos, las propiedades fotosensibilizantes de dos de los daños oxidativos del ADN, el 5-formiluracilo (ForU) y la 5-formilcitosina (ForC), poniendo especial énfasis en la capacidad de estos para poblar sus estados tripletes, así como de inducir la formación fotosensibilizada de dímeros ciclobutánicos de pirimidina (CPD). Por último, en el Capítulo 6 se ha desarrollado una nueva alternativa sintética para la incorporación del ForU en oligonucleótidos. Debido a la inestabilidad del grupo aldehído, esta síntesis se lleva a cabo generalmente mediante la incorporación de un precursor el cual es posteriormente convertido en el ForU mediante la acción de un agente oxidante. Por el contrario, en la nueva alternativa planteada el aldehído es protegido con un PPG, de manera que una vez insertado en el ODN, el aldehído es liberado de forma selectiva mediante el empleo de luz. Este trabajo supone un avance en el estudio de las propiedades fotosensibilizantes del ForU ofreciendo una nueva herramienta para la evaluación de las mismas en un entorno más cercano al del ADN. / [CA] L'espectre de la llum solar està compost per una àmplia gamma de radiacions electromagnètiques les quals tenen diferents impactes sobre la vida en la terra. Entre elles, les pertanyents a la regió ultraviolada prenen un paper principal quan ens referim a la fotobiologia, ja que poden interactuar amb les biomolècules per mitjà de processos tant directes com fotosensibilitzats. Com a resultat, aquestes biomolècules poden patir modificacions que no sempre tenen efectes beneficiosos. En este context, els danys fotoinduits a l'ADN són de gran rellevància ja que estan estretament relacionats amb la creixent incidència de càncer de pell. Per això, és necessari tant d'investigar els mecanismes involucrats en els processos com el desenvolupament de noves estratègies per a combatre'ls. En la present tesi es dóna resposta a aquestes necessitats per mitjà del desenvolupament i ús de grups protectors fotolàbils (PPG). En una primera part s'avança en el desenvolupament de nous PPG basats en filtres solars. Estos ofereixen l'avantatge d'actuar, una vegada alliberats, com un escut protector enfront de la radiació ultraviolada. En este context, en el capítol 3 s'aprofundeix en les propietats fotofísiques i fotoquímiques dels sistemes formats per l'avobenzona com PPG d'àcids carboxílics, més concretament del ketoprofé (KP) i del naproxé (NPX). En este estudi s'analitza per mitjà de modelatge molecular i tècniques espectroscòpiques la influència que té en el procés d'alliberament l'energia relativa del triplet de l'avobenzona en la seua forma dicetònica, 3AB(K)*, respecte a la dels compostos protegits. En esta mateixa línia de treball, en el capítol 4 s'ha desenvolupat un nou PPG capaç d'alliberar el filtre solar oxibenzona (OB) junt amb compostos carbonílics. En una segona part, el focus d'atenció s'ha posat en el concepte de "Cavall de Troia", el qual estableix que certes lesions de l'ADN poden actuar al seu torn com fotosensibilitzadors endògens generant així noves lesions en el seu entorn. En este context, en el capítol 5 s'han estudiat, per mitjà de mètodes tant experimentals com teòrics, les propietats fotosensibilitzants de dos dels danys oxidatius de l'ADN, el 5-formiluracil (ForU) i la 5-formilcitosina (ForC), posant especial èmfasi tant en la capacitat d'estos per a poblar els seus estats triplet, com d'induir la formació fotosensibilitzada de dímers ciclobutànics de pirimidina (CPD). Finalment, en el capítol 6 s'ha desenvolupat una nova alternativa sintètica per a la incorporació del ForU en oligonucleòtids. A causa de la inestabilitat del grup aldehid, esta síntesi es duu a terme generalment per mitjà de la incorporació d'un precursor el qual és posteriorment convertit en el ForU per mitjà de l'acció d'un agent oxidant. Al contrari, en la nova alternativa plantejada l'aldehid és protegit amb un PPG, de manera que una vegada inserit en l'oligonucleòtid, l'aldehid és alliberat de forma selectiva per mitjà de l'ús de llum. Este treball suposa un avanç en l'estudi de les propietats fotosensibilitzants del ForU i ofereix una nova ferramenta per a l'avaluació de les mateixes en un entorn més pròxim al de l'ADN. / [EN] The solar spectrum is composed of a wide range of electromagnetic radiations which have different impacts on life on earth. Among them, those belonging to the ultraviolet region are of utmost importance when we refer to photobiology, since they can interact with biomolecules through both direct and photosensitized processes. As a result, these biomolecules can undergo modifications that do not always have beneficial effects. In this context, photoinduced DNA damage is of great relevance as it is closely related to the increasing incidence of skin cancer. Therefore, it is necessary both to investigate the mechanisms involved in these processes and to develop new strategies to avoid them. In this Thesis these issues have been addressed through the development and use of photolabile protecting groups (PPG). The first part of this Thesis involves the development of new PPG based on solar filters. Once released, these PPG offer the advantage of acting as ultraviolet shields. In this context, Chapter 3 looks into the photophysical and photochemical properties of those systems formed by avobenzone as PPG of carboxylic acids, more specifically ketoprofen (KP) and naproxen (NPX). In this study, the influence on the photorelease process of the relative energetic location of the avobenzone triplet manifold in its diketo form, 3AB(K)*, with respect to that of its caged compound, is duly analyzed by means of molecular modeling and spectroscopic techniques. Following this same line of work, a new PPG capable of releasing oxybenzone (OB) solar filter along with carbonyl compounds has been developed in Chapter 4. The second part of this Thesis focuses on the "Trojan Horse" concept, which establishes that certain DNA lesions can act as endogenous photosensitizers, thus generating new lesions in their neighborhood. In this context, in Chapter 5 the photosensitizing properties of two oxidatively generated DNA damages, namely 5-formyluracil (ForU) and 5-formylcytosine (ForC), have been studied by means of experimental and theoretical approaches. Here, special emphasis has been placed on unraveling their capacity to photoinduce the formation of cyclobutane pyrimidine dimers (CPD). Finally, in Chapter 6 a new synthetic alternative for the incorporation of ForU into oligodeoxynucleotides (ODN) has been developed. Due to the instability of the aldehyde group, this synthesis is generally carried out by incorporating a precursor which is subsequently converted into ForU by the action of an oxidative agent. On the contrary, in the new approach, the aldehyde is protected with a PPG, so that once inserted into the ODN, the aldehyde is selectively released through the use of light. This work entails a step forward in the study of the photosensitizing properties of ForU, offering a new tool for their evaluation within the DNA environment. / Lineros Rosa, M. (2021). Photoremovable protecting groups for carbonyl compounds of biological interest [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/167764 / TESIS

No description available.

Im interested in the topic of praying machine, because I want to analyze aspects of photography and its functions. It's known, that the reality is manipulated by photography. Bud we can also say, that the relationship between reality and photography is neutral in fact, that the manipulation is made by our interpretation of photography. The change of the reality can be realized just in the dialog between photography and reality. Can it be, that the mechanization change into the will? Does it prays praying mill or the buddhistic monk, who rotates the mill? When he believes into it, is it enough? Or is it enough if believes who watch the monk with his mill? ... The computers from he place A are "praying" the prayers from the place B. With Tomáš Javůrek we collaborated with Vladimír Veselý and Radek Lát to create the Game for re-articulation our reality on the base of the revision of our faith.