Bottlebrush polymers are interesting topologies that have become increasingly relevant in various applications including rheology modifiers, super-soft elastomers, photonic crystals, anti-fouling coatings, the in vivo delivery of therapeutic agents, and as promising substrates in lithographic printing. These macromolecules are comprised of numerous polymeric side-chains densely grafted to a polymer backbone. The densely grafted nature of bottlebrush polymers results in steric repulsion between neighboring polymer chains, forcing these macromolecules to adopt a chain-extended conformation. Although these remarkable macromolecules have a many different applications, the transformative potential of the bottlebrush polymer topology has not been realized because the synthesis of high molecular weight bottlebrush polymers is challenging. This dissertation focusses on improving the synthesis of these large macromolecules using the grafting-through strategy in the first section and the transfer-to strategy in the second section. For the first time the effect of anchor group chemistry—the configuration of atoms linking the polymer to a polymerizable norbornene—was studied on the kinetics of ring-opening metathesis polymerization (ROMP) of macromonomers (MMs) initiated by Grubbs 3rd generation catalyst. A variance in the rate of propagation of >4-fold between similar MMs with different anchor groups was observed. This phenomenon was conserved across all MMs tested, regardless of solvent, molecular weight (MW), or repeat unit identity. Experimental and computational studies indicated that the rate differences likely resulted from a combination of varying steric demands and electronic structure among the different anchor groups. This new insight will allow others to achieve high MM conversion and prepare pure, high MW bottlebrush polymers by ROMP grafting-through. The second section of this dissertation deals with a little studied bottlebrush synthesis technique called the transfer-to method. This method is a hybrid of the grafting-from and grafting-to approaches in which the growing polymer side chains detach from the backbone, propagate freely in solution, and then reattach to the backbone in a chain transfer step. Several parameters were investigated to determine optimal conditions for this process. This study provides for the first time a guide to use the transfer-to method to produce high purity bottlebrush polymers with controllable backbone and side chain length. / Ph. D. / Bottlebrush polymers are interesting topologies that have become increasingly relevant in various applications including super-soft elastomers and drug delivery agents. These macromolecules are comprised of numerous polymeric side-chains densely grafted to a polymer backbone. The densely grafted nature of bottlebrush polymers results in steric repulsion between neighboring polymer chains, forcing these macromolecules to adopt a chain-extended or worm like conformation. Although these remarkable macromolecules have a many different applications, the transformative potential of the bottlebrush polymer topology has not been realized because the synthesis of large bottlebrush polymers is challenging. This dissertation focusses on improving the synthesis of these big macromolecules using the grafting-through strategy in the first section and the transfer-to strategy in the second section. For the first time the effect of anchor group chemistry—the configuration of atoms linking the polymer to a polymerizable norbornene—was studied on bottlebrush synthesis. A variance in how fast the polymerization took between similar MMs with different anchor groups was observed. Experimental and computational studies indicated that the differences likely resulted from a combination of varying steric demands and electronic structure among the different anchor groups. This new insight will allow others to achieve high MM conversion and prepare pure, high MW bottlebrush polymers by ROMP grafting-through. The second section of this dissertation deals with a little studied bottlebrush synthesis technique called the transfer-to method. This method is a hybrid of two well-known methods, grafting-from and grafting-to approaches, in which the growing polymer side chains detach from the backbone, polymerize freely in solution, and then reattach to the backbone in a chain transfer step. Several parameters were investigated to determine optimal conditions for this process. This study provides for the first time a guide to use the transfer-to method to produce high purity bottlebrush polymers with controllable sizes.

Dual-comb spectroscopy (DCS) has widespread applications. It has become a more prominent spectroscopic tool because it has broad spectral coverage with high frequency resolution. We demonstrate the broadband and high resolution of DCS to probe transient events, showing the rst use of DCS of laser-induced plasmas (LIPs). Our measurements span absorption features 7 THz wide, simultaneously detecting Rb D2, K D1 and D2 absorption lines with the ability to resolve the isotope ratios in the Rb D2 line. This technique is more broadband and faster than tunable laser absorption spectroscopy because it eliminates the requirement to scan across transitions. Additionally, DCS makes higher resolution measurements than laser-induced break- down spectroscopy. Our ultimate goal is to use DCS as a technique to ascertain the chemical composition of unknown samples. Our rst demonstration of this technique illustrates that DCS makes broadband, high-resolution measurements with the ability to measure isotope ratios, which is necessary for determining sample composition.

Os MEMS (Micro Electro Mechanical Systems) compõem uma tecnologia que tem ganhado destaque nas últimas décadas e sua difusão reflete um constante crescimento tanto em aplicações quanto em volume financeiro envolvido. Um MEMS de fundamental importância é o comb-drive. Várias são as áreas da indústria que se beneficiam das virtudes deste microdispositivo. Confiabilidade, invisibilidade e economia de energia são as principais qualidades desses sistemas. Os produtos desta tecnologia representam um mercado emergente e que movimenta bilhões de dólares anuais, contudo, há de se considerar a crescente exigência no quesito qualidade por parte daqueles que a utilizam. A forma como estes dispositivos tem sido testados, por amostragem, não garante esta qualidade com a segurança desejada. Também cabe destacar que os testes precisam ser realizados de forma rápida e com baixo custo. Este trabalho objetiva investigar um modelo matemático que expresse uma dinâmica próxima daquela observada em MEMS, visando contribuir para agilidade e qualidade dos testes. A técnica utilizada para encontrar os regressores e o emprego de modelos não-lineares são as principais diferenças deste trabalho em relação aos comumente encontrados na literatura no âmbito de MEMS. As técnicas utilizadas são oriundas da identificação de sistemas. Por se tratar de dispositivos com dimensões micrométricas, a coleta de dados reais torna-se inviável. Assim, os dados foram obtidos através de ensaios em uma plataforma de testes elaborada no software ANSYS®. De posse desses dados e considerando a estrutura do modelo NARX foi possível a elaboração de uma série de modelos, cada um deles com alguma diferença na estrutura. O método dos mínimos quadrados foi o escolhido para estimação dos parâmetros. Os resultados obtidos para cada modelo foram comparados aos coletados na plataforma. Esta comparação se deu na forma qualitativa e quantitativa e com base nisso foi possível identificar um modelo matemático acurado para a dinâmica não linear de dispositivos MEMS. / 98 f.

A tecnologia MEMS (Micro-Electro-Mechanical Systems)é inovadora e destaca-se pela ilimitada gama de aplicações, especialmente na concepção de sensores e atuadores. Dessa forma, os MEMS vêm despertando elevado interesse industrial e com isso agregam investimentos significativos, movimentando um mercado de bilhões de dólares anuais. Todavia, as exigências industriais apresentam tendências cada vez mais rigorosas no que se refere à qualidade dos dispositivos. Neste sentido, a qualidade de MEMS é assegurada através da etapa em que os dispositivos são testados. Com o emprego de técnicas de microusinagem, milhões de dispositivos são fabricados em uma única lâmina de silíticio. Entretanto, sabe-se que os processos utilizados na fabricação ainda apresentam limitações. Assim, são confeccionados estruturas avariadas que apresentam falhas durante a operação. Desta forma, o colapso de vigas em elastomassas de microrrotores tem sido uma problemática constante. Assim, torna-se necessário desenvolver métodos que favoreçam a identificação desses defeitos antes da comercialização. Este trabalho tem por objetivo a detecção do colapso em vigas de elastomassas através da técnica de signature. Foi realizado um estudo de três tipologias diferentes do núcleo deformável do atuador comb-drive. As elastomassas foram modeladas com o método dos elementos finitos no software ANSYS (Analysis System). Foram realizadas simulações do comportamento da estrutura intacta e danificada para a coleta dos dados referentes a força f(t) e deslocamento x(t). Com os dados coletados, criou-se um banco de assinaturas referente ao comportamento das elastomassas atuando de forma intacta e sob colapso. Para gerar as assinaturas, foi empregado o principio de defasagem das Figuras de Lissajous, buscando associar a singularidade geométrica das assinaturas ao colapso. Assim, para essa finalidade, utilizou-se a ferramenta computacional MATLAB (MATrix LABoratory). Através da análise qualitativa dos resultados obtidos, verificou-se tanto a possibilidade de detecção do colapso nas três tipologias quanto a identificação da viga fraturada para cada uma. / 132 f.

This thesis explores the generation and the coherence properties of Raman frequency combs that are initiated from vacuum fluctuations using hydrogen-filled hollow-core photonic crystal fibre (HC-PCF). The motivation is to explore a novel route for generating attosecond pulses and waveform synthesis. To this end, work has been undertaken in the design and fabrication of HC-PCF, in the generation of Raman comb with a compact set-up and finally in an experimental demonstration of the mutual coherence between the comb spectral components. Here, the well-established photonic bandgap (PBG) HC-PCF is further developed. Surface mode spectral positions are controlled by chemical etching technique, and a single piece of fibre with two robust bandgaps is fabricated. Furthermore, the second established class of HC-PCF; namely large-pitch Kagome-lattice HC-PCF, has experienced challenging developments. This led to the fabrication of a hypocycloid-core seven-cell Kagome HC-PCF with comparable attenuation value to that of PBG HC-PCF while offering much larger bandwidth. Using the fabricated HC-PCF, different Raman frequency comb systems are developed. In addition to the previously-generated multi-octave Raman frequency comb from a large 1064 nm Nd:YAG Q-switch laser, several more compact version of Raman comb sources have been developed, including one whose lines lay in the visible and UV for applications in forensics and biomedicine. The Raman frequency comb generated inside a length of hydrogen-filled HC-PCF is further investigated by studying the coherence of the Raman lines. Despite of vacuum-fluctuation-initiation, it is demonstrated that the comb has self- and mutualcoherence properties within each single shot, bringing thus the possibility of generating attosecond pulses with non-classical properties.

The first topic of the thesis presents an NTSC digital video decoder which is designed by using two lines delay comb filter to decode the luminance signal (Y) and the chrominance signal (C). The coefficients of the low pass filter are tuned properly to reduce the gate count without losing any original performance of the chroma demodulator. The second topic of the thesis is to propose a method and a circuitry to resolve the out-of-phase problem between the color burst and the sub-carrier in NTSC TV receivers. The feature of the method is that a delay means is inserted which leads to the synchronization of the color burst and the sub-carrier such that the following color demodulator is able to extract right color signals. Besides, the locking of the two signals will be fastened without any extra large circuit cost.

Bees interested people because of honey and wax from ancient times. They were called God’s beetles, God’s workers. Bee products were used for food and medicine. It is advisable for people to eat about 1,8 kg of honey a year. Lately bee farms have been growing stronger. The owners of some apiaries are increasing and modernizing their farms. At the moment 83 thousand families are bred in Lithuania. AIM OF RESEARCH. To establish the dependence of bee mass on the springs of comb, comparing the used discs of the springs of the bee family natural wax combs an artificial combs. METHODS AND CONDITIONS OF RESEARCH. The data for research were collected during the summer of 2006 from bee families bred in Kaunas. In individual variants hives were expanded by discs of springs of natural wax comb and plastic discs of springs of combs. After 8 days after making of cells they were put into well warmed hives or a thermostat for breeding. After 24-36 hours after breeding of bees they were weighed. This experiment will negate the widely spread groundless statements that plastic combs influence the mass of bees. Apirians may safely use plastic wax discs for making combs for bee families. CONCLUSIONS: 1. Artificial discs are more accurate that natural wax discs in all directions of the cells of the comb. 2. Wax discs and artificial comb discs do not influence the mass of bees, as bees bred on such discs during the research showed no significant differences.

No description available.

This thesis presents research into ultra-low noise photonic microwave synthesis and the development of a novel, frequency comb-based, fibre optic time transfer technique. The focus in the first area is on reducing the noise introduced in the optical-to- electrical conversion process using balanced optical-microwave phase detectors. Two mainly free-space and two mainly fibre-based devices were built and their performance was characterised. The phase noise of the optical-to-electrical conversion of the free-space device was -119 dBc Hz⁻¹ at 1 Hz and -143 dBc Hz⁻¹ at 20 kHz from an 8 GHz carrier which is the best performance reported for a free-space balanced-optical microwave phase detector. The improved fibre-based set-ups demonstrated a state-of-the-art amplitude-to-phase noise suppression of 60 dB and a phase noise of the optical-to-electrical conversion of -131 dBc Hz⁻¹ at 1 Hz and 148 dBc Hz⁻¹ at 20 kHz from an 8 GHz carrier. The novel time transfer technique developed in the second part superimposes timing information onto the optical pulse train of an ITU-channel-filtered frequency comb using an intensity modulation scheme. Time transfer over a 50 km long, delay-stabilised fibre spool produced a state-of-the-art time deviation of 300 fs and an accuracy of approximately 0.01 ns which is close to the best performance achieved using amplitude modulated cw lasers. Using this technique on a 159 km long installed fibre link between NPL and Reading, the same time deviation was achieved and an accuracy of approximately 0.08 ns was obtained, limited by uncertainty of the time interval counter. Using the same fibre link, microwave frequency transfer of the ITU-channel-filtered comb was demonstrated with a fractional frequency instability of 2x10⁻¹⁷ at 5000 s which is approximately at the same level as the best previously reported results which were obtained with a 30 nm wide optical frequency comb.

The role of the queen in wax secretion and comb building was studied in the the Cape honeybee, Apis mellifera capensis (Escholtz). The percentage of bees bearing wax and the amount of wax borne by these bees did not differ between the experiments. This meant that the queenless and queenright colonies had the potential to construct equal amounts of comb as the amounts of wax available for comb building was the same. Contrary to this prediction, queenright colonies constructed 8 times more comb than their queenless counterparts. Queenright Apis mellifera scutellata colonies constructed 4 times more comb than their queenless counterparts. The increased amount of 9-oxo-2-decanoic acid (90DA) in the A.m.capensis mandibular gland secretions could not alone account for this difference. In fact, A.m.capensis and A.m.scutellata colonies constructed similar amounts of comb when they were given their own queens or queens from the other race. Worker bees need to have direct contact with their queen for comb building to be enhanced. Even when the queen had her mandibular glands extirpated and tergite glands occluded large amounts of comb were constructed than when access to the queen was limited. Direct access to the head of a mated queen proved to be the stimulus enhancing comb building. No comb was constructed when the workers had access to the abdomen of the queen. Virgin queens did not stimulate comb building. The relatively large amounts of 90DA and 9HDA from the mandibular glands of Cape virgin queens had not influenced comb building. Worker sized cells were generally constructed. These cells were slightly smaller than those constructed by European honeybees, but were indicative of African bees. A few queen less colonies constructed cells that were of an intermediate drone and worker size. Four mandibular gland pneromones were measured by gas chromatography. No correlations between these pheromones and the comb construction measurements were found. It is unlikely that the mandibular gland pheromones are the only pheromones that stimulate comb building. Pheromones from other glands on the head may contribute towards the enhancement of comb building, and they are not present in virgin queens