This thesis describes the use of short external cavity (SXC) semiconductor diode lasers as single longitudinal mode (SM) tunable sources. A SXC forces a multimode diode laser to lase on a single longitudinal mode. Various laser types were investigated in SXC configurations using both planar and spherical external mirrors. The side mode suppression ratio (SMSR) and the SM tuning range were measured with respect to the positioning of the external cavity element. With a planar mirror as the SXC element, SMSR of —33 dB and SM tuning ranges of 1 nm (110% of a mode spacing) were obtained with inverted rib waveguide (IRW) lasers. For external cavity lengths of ~ 60 um the total continuous SM tuning range summed over all modes was found to be 72 cm^-1 or 12 nm. The use of a spherical mirror improved the results. A SXC laser consisting of a spherical mirror and an IRW laser had SMSR values of —37 dB and SM tuning ranges of 1.10 nm. Power and voltage characteristics of SM SXC lasers were also examined. It was found possible to use the laser voltage and electronic feedback to control the external cavity length for optimum SM output. The external differential quantum efficiency (DQE) was found to be wavelength dependent and may be explained by the wavelength dependence of the scattering/absorption loss. One aspect of the characteristic trend of the DQE with respect to wavelength is that it offers the possibility of determining the lasing wavelength of the SM without the use of a monochromator. / Thesis / Master of Engineering (ME)

Yes / There are many human oral antimicrobial peptides responsible for playing important roles including maintenance, repairing of oral tissues (hard or soft) and defense against oral microbes. In this review we have highlighted the biochemistry, physiology and proteomics of human oral histatin peptides, secreted from parotid and submandibular salivary glands in human. The significance of these peptides includes capability for ionic binding that can kill fungal Candida albicans. They have histidine rich amino acid sequences (7–12 family members; corresponding to residues 12–24, 13–24, 12–25, 13–25, 5–11, and 5–12, respectively) for Histatin-3. However, Histatin-3 can be synthesized proteolytically from histatin 5 or 6. Due to their fungicidal response and high biocompatibility (little or no toxicity), these peptides can be considered as therapeutic agents with most probable applications for example, artificial saliva for denture wearers and salivary gland dysfunction conditions. The objectives of current article are to explore the human histatin peptides for its types, chemical and biological aspects. In addition, the potential for therapeutic bio-dental applications has been elaborated. / King Saud University

Cavity-nesting guilds are diverse communities of organisms that are hierarchically structured around the creation of and competition for tree holes as nest sites. Quantifying these communities as networks of interconnected species, or "nest webs", is a proven and efficient method for identifying important species and interactions within a cavity-nesting guild that can aid the management of these often threatened communities. Yet nest web data does not provide information regarding how natural resource managers are to encourage the support and adoption of conservation behaviors. This dissertation comprises two broad studies: one describing a cavity-nesting guild in central Namibia, and the other exploring methodology for identifying an effective flagship species for local conservation. In chapter 1, I provide background information of my study system and a review of the cavity-nesting and flagship species literature. In chapter 2, I quantify the species and resources within a cavity-nesting guild and create a cavity nest web to depict cavity creation and use in central Namibia. All cavity-nesters depended on sparse, large trees, which likely contributed to limited use of tree species across the guild. Cavity-excavators were of disparate importance for secondary cavity-nesters: important for small- and medium-bodied species but mostly unimportant for large-bodied species who depend more on large trunk hollows. In chapter 3, I describe and compare species-specific cavity resource niches among guild members to explore potential instances of cavity resource partitioning. Use of nest cavities appears to sort out by size among both cavity-excavators and secondary cavity-nesters. Excavators appear to partition cavity substrate spatially by decay class, while spatial partitioning among secondary nesters was largely by cavity type. Most interesting is the apparent temporal partitioning of large excavations among medium- and large-bodied cavity-nesters. In chapter 4, I explore a novel approach to flagship species selection that identified all previously-existing traits for flagship species, numerous traits specific to culture and personal experience, and a dozen new traits that were previously not recognized as potentially important for flagship species. This method shows considerable promise as a tool for investigating preferences for wildlife among broad stakeholders, as well as for engaging local people in wildlife conservation. / Doctor of Philosophy / Holes in trees, or cavities, are important resources for many birds, who use cavities as a safe place for raising young. Cavity-nesting birds are linked together in a cavity "nest web" based on the types of cavities used by each species. Understanding how birds are linked with each other and with certain types of cavities is critical in order to design conservation plans that preserve important community relationships. However, successful conservation also depends on strong support from local people, who are most often the people tasked with implementing the conservation actions. Flagship species can be used to gain support from necessary groups of people for specific conservation missions. This dissertation consists of two broad studies: the first study describes a community of cavity-nesting birds in Namibia, and the second explores a new way to investigate how people connect with wildlife through emotional connections. In chapter 1, I provide background information on my area of research. In chapter 2, I outline the different trees, cavities, and birds at the study site and estimate their abundance in the area. I also create a cavity nest web that illustrates the links between species. Large trees were relatively uncommon, but were important for all birds in the community. Cavities made by other birds, such as woodpeckers, were very important for small- and medium-sized species, but were mostly unimportant for large-sized species. In chapter 3, I compare the tree cavities used by different species, including the types of trees, cavities, and cavity sizes. I also explore multiple ways by which cavity-nesting birds might be dividing cavities between different species. Our most interesting finding was how medium-sized species seem to share cavities in time rather than in space; some species (i.e., small owls and woodpeckers) breed before some larger species that use the same type of cavity. Breeding early may be a way for some species to avoid competition with more competitive species, and may be the first example of this strategy being used by multiple cavity-nesters in a community. In chapter 4, I explore a new method for selecting flagship species. This method uncovered all traits that have been previously recommended for flagship species, as well as many traits specific to culture and personal experience. We also identified a dozen new traits that were previously not considered to be important for flagship species. Our new method is very promising as a tool for investigating preferences for wildlife among broad stakeholders, and for engaging and involving local people in wildlife conservation.

In the field of optical fiber sensors, one of the most versatile structures is the Fabry-Perot interferometer. This thesis will present a novel sensor based on an Intrisnic Fabry-Perot Inferferometer (IFPI) cavity to measure axial acceleration, refractive index, and temperature. The sensor structure is based on previous work done by R. Wang at the Center for Photonics Technology. This work suggests its flexibility in many different roles with a sensitivity to axial acceleration of 70 pm/unit of acceleration, to refractive index of 60 nm/Refractive Index Unit, and to temperature of 7.8 pm/°C. Future work is also discussed in measuring tangential acceleration with direction using a PM fiber as the lead-in and observing the reflections on the slow and fast axes. / Master of Science

<p>The fundamental design of axial compressors has matured to an exceptional level of performance due to a century of research. With the improvements in efficiency becoming increasingly difficult, attention continues to be channeled towards understanding and reducing secondary losses such as hub or tip clearance leakages, seal leakages, etc. Studies detailing the impact of seal leakages are relatively scarce due to difficulties of obtaining data in the complex rotating geometries of a high-speed compressor cavity. While the impact of seal leakages on primary passage is readily available, details inside the cavity geometry is scarce in open literature because majority of the investigations have been performed on linear cascades with slots machined as cavities or standalone labyrinth seals that fail to provide a wholesome understanding of the leakage flow and windage heating in the rotating geometries.<br></p> <p> Therefore, the principal objective of this work is to investigate flow physics in the stator cavity wells for understanding the flow path of the leakage fluid and windage heating within the cavity. A parametric model of the Purdue 3-Stage Compressor (P3S) is used to allow for rapid geometric modifications to the seal clearances in a coupled stator-cavity system. The investigations presented here consist of a series of numerical simulations using ANSYS CFX as the primary Computational Fluid Dynamics (CFD) tool. Measurements performed by previous investigators are utilized to define the boundary conditions of this model. This study’s goal is to characterize the interdependence of parameters such as cavity leakage flow rate, circumferential velocity, and windage heating for understanding the flow structure inside the cavity wells and their impact on cavity temperatures. Data acquired is intended to reveal mechanisms through which cavity leakage flows affect the stator passage aerodynamics and the windage heating, both regarding their effect on the compressor performance and the details of the flow path within the cavity. Consequently, this will provide insight into how the complex cavity leakage flow influences the design considerations for optimizing stator passage aerodynamics and minimizing stator cavity heating.</p> <p>The compressor operating conditions of Nominal Loading (NL) is the focus of this CFD work since the flow field at High Loading (HL) has significant boundary layer separation. NL is closest to both the design and peak efficiency conditions where the compressor would spend the majority of its time in operation, understanding cavity flow physics at this operating condition would have a direct impact on enhancing the overall compressor performance. A CFD model of the standalone primary passage is developed first using the dataset available from experiments performed by previous investigators for establishing confidence in the primary passage flow physics. Therefore, detailed total pressure, total temperature, velocity, and flow angle data collected behind each blade row is utilized for validating the primary passage flow in the CFD model. After validating the primary passage model, measurements in the coupled cavity model are acquired to understand the flow variations as well as temperature development in the cavity due to the varying labyrinth seal clearance.</p> <p>The investigations in this work are divided into two distinct branches. First, to aid the aerodynamic research community, the flow structure inside the cavity wells is investigated to understand the impact cavity leakage flow has on the compressor efficiency and on its interactions with the primary flow path. Secondly, for understanding the development and rise of temperature in the cavity wells, i.e., the windage effect, are performed to aid the thermo-mechanical research community so that the material choices and stress analysis of the cavity components can be optimized. Hence, the trends in the data acquired provide the aerodynamic, mechanical, and secondary flow system designers an indication of the complexities of the flow within shrouded stator cavities and provide insight into designing and optimizing more complex geometries.</p><p>Results from this investigation describe how increasing seal clearance deteriorates the stator performance and enables the cross-passage migration of low momentum fluid to worsen hub corner separation. The simulations also state the case for re-ingestion at tight seal clearances as the 3D streamlines show heated efflux emerges from the upstream cavity interface, dwells near the hub, and gets recirculated back into the cavity inlet well. Radial variations inside the cavity wells show high cavity temperatures with excessive cavity due to re-ingestion, while the cases that avoid re-ingestion are observed at the lowest temperatures. These radial variations also identify the cavity leakage flow path and the development of circumferential velocity. Lastly, the total pressure loss, total temperature rise and windage heating, all show a strong dependence on circumferential velocity development, which is inherently dependent on the labyrinth seal clearances.<br></p>

Strong coupling of light and matter is an essential element of cavity quantum electrodynamics (cavity-QED) and quantum optics, which may lead to novel mixed states of light and matter and to applications such as quantum computation. In the strong-coupling regime, where the coupling strength exceeds the dissipation, the light-matter interaction produces a characteristic vacuum Rabi splitting. Therefore, strong coupling can be utilized as an effective coherent interface between light and matter (in the form of electron charge, spin or superconducting Cooper pairs) to achieve components of quantum information technology including quantum memory, teleportation, and quantum repeaters. Semiconductor quantum dots, nuclear spins and paramagnetic spin systems are only some of the material systems under investigation for strong coupling in solid-state physics. Mixed states of light and matter coupled via electric dipole transitions often suffer from short coherence times (nanoseconds). Even though magnetic transitions appear to be intrinsically more quantum coherent than orbital transitions, their typical coupling strengths have been estimated to be much smaller. Hence, they have been neglected for the purposes of quantum information technology. However, we predict that strong coupling is feasible between photons and a ferromagnetic nanomagnet, due to exchange interactions that cause very large numbers of spins to coherently lock together with a significant increase in oscillator strength while still maintaining very long coherence times. In order to examine this new exciting possibility, the interaction of a ferromagnetic nanomagnet with a single photonic mode of a cavity is analyzed in a fully quantum-mechanical treatment. Exceptionally large quantum-coherent magnet-photon coupling with coupling terms in excess of several THz are predicted to be achievable in a spherical cavity of ∼ 1 mm radius with a nanomagnet of ∼ 100 nm radius and ferromagnet resonance frequency of ∼ 200 GHz. This should substantially exceed the coupling observed in solids between orbital transitions and light. Eigenstates of the nanomagnet-photon system correspond to entangled states of spin orientation and photon number over 105 values of each quantum number. Initial coherent state of definite spin and photon number evolve dynamically to produce large coherent oscillations in the microwave power with exceptionally long dephasing times of few seconds. In addition to dephasing, several decoherence mechanisms including elementary excitation of magnons and crystalline magnetic anisotropy are investigated and shown to not substantially affect coherence upto room temperature. For small nanomagnets the crystalline magnetic anisotropy of the magnet strongly localize the eigenstates in photon and spin number, quenching the potential for coherent states and for a sufficiently large nanomagnet the macrospin approximation breaks down and different domains of the nanomagnet may couple separately to the photonic mode. Thus the optimal nanomagnet size is predicted to be just below the threshold for failure of the macrospin approximation. Moreover, it is shown that initially unentangled coherent states of light (cavity field) and spin (nanomagnet spin orientation) can be phase-locked to evolve into a coherent entangled states of the system under the influence of strong coupling.

This thesis presents a theoretical study of the collective effects of a large number of photon emitters coupled to optical cavities. The ensemble effects are accounted for by considering both the light emitting and scattering by the photon emitters. It suggests that, to correctly estimate the emitters ensemble coupled cavity mode, it is necessary to consider the existence of the excited excitons ensemble and optical pumps. This thesis shows that optical pumps can excite more excitons and scattering channels as pumping power increases. The change in exciton population can lead to comprehensive spectral behaviors by changing the cavity spectral shapes, bandwidth and resonance positions, through the inhomogeneous broadening and frequencies repulsion effects of collective emissions. The existence of the exciton ensemble can also enhance optical coupling effects between target excitons and the cavity mode. The target exciton, which has a relatively large coupling strength and is close to the cavity peak, can affect the properties of the background dipoles and their coupling to the cavity. All these collective effects are sensitive to the number, the resonances distribution, and the optical properties of the background excitons in the frequency domain and the property of the target exciton, if any. This study provides a perspective on the control of the optical properties of cavities and individual excitons through collective excitation. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-07-30 14:51:15.914

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vii, 45 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 32-37).

Thesis (M.S.)--University of Michigan, 1986.

Thesis (M.S.)--University of Michigan, 1969.