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This thesis deals with two independent topics. The first is focused on the study of reversible covalent interactions of a carbonyl group with alcohols and water forming hemiacetals (respectively hydrate) derived from pyrazine trifluormethylketone. The main research method in this part is the NMR spectroscopy and experimental results are also supported by quantum chemical calculations. The second topic aims to the preparation and the study of photochemical properties of three dihydropyrazines which exhibit fluorescence both in solution and solid phase. The fluorescence can be influenced by means of complexation by various metal ions. Prepared dihydropyrazines also show interesting values of the Stokes shift. The structure of these new compounds was confirmed by X-ray analysis.

Thesis advisor: Jianmin Gao / With the rapid evolution of antibiotic resistance, the need for more effective antibiotics is imminent. Bacterial membranes are an appealing target due to their accessibility and relatively conserved structures. Membrane targeting antibiotics, especially cationic antimicrobial peptides (CAMPs) such as host defense peptides, have been increasingly explored as novel antibiotics and tunable innate antimicrobials. The latter could be achieved by treatment with an antibiotic adjuvant: a compound that would increase the potency of host CAMPs without killing the bacteria on its own. Boosting the host’s own immune system with an adjuvant is beneficial over using antibiotics and would theoretically avoid triggering bacterial resistance. One mechanism of bacterial resistance is increasing the cationic charge of the membrane. As CAMPs are electrostatically attracted to anionic bacterial membranes, making the membrane more cationic decreases that attraction, rendering CAMPs less effective. To target this resistance mechanism chemically, two antibiotic adjuvant strategies were explored as co-treatments with various CAMPs: membrane targeting peptides used to bind and block surface amines, and small molecules used to either acetylate surface amines or convert a cationic membrane phospholipid to an anionic phospholipid. Co-treatment of the Staphylococcus aureus (S. aureus) membrane targeting peptide KAM-CT and various CAMPs increased S. aureus susceptibility to those CAMPs. Bacterial surface acetylation using sulfo-NHS-acetate followed by CAMP treatment caused up to 10 times increased CAMP potency. Hydrazine and hydroxylamine were shown to cleave the lysine moiety from the lysyl-phosphatidylglycerol (Lys-PG) phospholipid to generate phosphatidylglycerol (PG) in liposome models. S. aureus was treated with a hydroxylamine-CAMP conjugate, but it showed decreased antibiotic activity compared to the CAMP alone. To better understand what was happening in the bacteria, a novel Lys-PG quantification protocol was created by fluorophore labeling Lys-PG and quantifying the labeled Lys-PG via normal phase high-performance liquid chromatography (NP-HPLC). Cyclic peptides, such as KAM-CT, represent complex yet synthetically attainable moieties that could be used as novel antibiotics adjuvants. Expanding the repertoire of reversible covalent chemistries, especially those applied to peptide cyclization, is desirable due to the high potency and selectivity of such interactions. Herein, we also describe a novel reversible covalent chemistry between 2-formylphenylboronic acid (FPBA) and 2,3-diaminopropionic acid (Dap): the imidazolidino boronate (IzB) conjugate. It was found to be potent (Kd = 100 μM) and quickly reversible (t1 = ~6 sec) under physiological conditions. IzB formation was successfully employed as a peptide cyclization strategy as there was little interference from biologically relevant small molecules, except cysteine. Cysteine interference was utilized to create “smart” peptides that can linearize upon increasing cysteine concentrations via thiazolidino boronate (TzB) formation with the FPBA moiety in the peptide. Such “smart” peptides could be used as pH-responsive peptides or cysteine sensors able to report on the cysteine concentration in complex media. / Thesis (MS) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

A major function assessed by Nature is the transport of a cargo between two different media, such as anions through cell membranes. Mimicking this function using complex systems is one of the biggest challenge of supramolecular chemistry. Metallo-organic cages are an important breakthrough in the encapsulation and transport of small molecules, providing a crucial platform for the development of systems chemistry. Binding a network member within a tetrahedral cage allows it to be hidden and then revealed upon receipt of a release signal, or transported as a cargo between spatially distant parts of a network. Larger capsules may also isolate subsystems from each other in the manner of vesicles. These dynamic architectures are synthesised by self-assembly, which involves the simultaneous formation of multiple coordinative and dynamic covalent linkages during the same overall synthetic process. Their shape and binding properties can be tuned by changing the subcomponents such as metals or ligands. Great progress has been reported in recent years in the development of three-dimensional cages that can interact with specific guest species, but there are limitations associated with the transport of these systems. Recent work by Nitschke et al. have successfully addressed practical separations problems by transporting a tetrahedral cage and its cargo from water into an ionic liquid layer. However, this system is not ideal as the process is triggered by an anion exchange not by a direct stimulus. This thesis reports the synthesis of an ionic liquid inspired tetrahedral system achieving reversible transport between water and an immiscible organic solvent driven by a change in temperature. Once the switchable capsules were obtained and characterised, their ability to move between different solvent phases upon heating was investigated. A capsule-mediated transport system as developed that is both directional and reversible. The flow of the capsule and its encapsulated cargo is directed using stimuli such as temperature modification. Ultimately an apparatus that allows the switchable capsules to move along a channel has been developed.

Digital watermarking of multimedia content has been proposed as a method for different applications such as copyright protection, content authentication, transaction tracking and data hiding. In this thesis, we propose a lossless watermarking approach based on Discrete Cosine Transform (DCT) for a new application of watermarking. A depth map obtained from a stereoscopic image pair is embedded into one of the two images using a reversible watermarking algorithm. Different from existing approaches which hide depth map in spatial domain, the depth information is hidden in the quantized DCT domain of the stereo image in our method. This modification makes the watermarking algorithm compatible with JPEG and MPEG-2 compression. After the investigation of the quantized DCT coefficients distribution of the compressed image and video, The bit-shift operation is utilized to embed the depth map into its associated 2D image reversibly for the purpose of achieving high compression efficiency of the watermarked image and/or video and high visual quality of stereo image and/or video after the depth map is extracted. We implement the proposed method to analyze its performance. The experimental results show that a very high payload of watermark (e.g. depth map) can be embedded into the JPEG compressed image and MPEG-2 video. The compression efficiency is only slightly reduced after the watermark embedding and the quality of the original image or video can be restored completely at the decoder side.

Digital watermarking of multimedia content has been proposed as a method for different applications such as copyright protection, content authentication, transaction tracking and data hiding. In this thesis, we propose a lossless watermarking approach based on Discrete Cosine Transform (DCT) for a new application of watermarking. A depth map obtained from a stereoscopic image pair is embedded into one of the two images using a reversible watermarking algorithm. Different from existing approaches which hide depth map in spatial domain, the depth information is hidden in the quantized DCT domain of the stereo image in our method. This modification makes the watermarking algorithm compatible with JPEG and MPEG-2 compression. After the investigation of the quantized DCT coefficients distribution of the compressed image and video, The bit-shift operation is utilized to embed the depth map into its associated 2D image reversibly for the purpose of achieving high compression efficiency of the watermarked image and/or video and high visual quality of stereo image and/or video after the depth map is extracted. We implement the proposed method to analyze its performance. The experimental results show that a very high payload of watermark (e.g. depth map) can be embedded into the JPEG compressed image and MPEG-2 video. The compression efficiency is only slightly reduced after the watermark embedding and the quality of the original image or video can be restored completely at the decoder side.

To study engineering can be difficult, especially transforming theoretical knowledge into practice. To address this issue, Otto and Wood have developed a reverse engineering and redesign methodology, suggesting that it can be used as a tool in the process of learning mechanical engineering and design. The aim with this report is to evaluate this statement, emphasizing on the reverse engineering process and evaluating its usefulness as an educational tool. In order to fully understand the process, two cordless screwdrivers will be reverse engineered, functioning as an example throughout the report. A theoretical background of the process will be introduced, including descriptions concerning the different steps and their encompassed tools, tests and methods. Trough the implementation, the screwdrivers are disassembled, analysed and experienced, resulting in a clear product specification with information of components and product functions. One example is the assembly plan, were the product structure is presented as two subassemblies with “layer on layer” assembly. Another result of the implementation is that the reverse engineering process was experienced in reality, exposing the required modifications necessary in order to function as an educational tool. The main issue for the process is its focus on customer needs instead of product focus. Therefore, it is suggested that a new reverse engineering process based on the existing one should be developed, focusing more on the product and less on the customer to better suit an educational purpose.

No description available.

Reversible watermarking techniques extract the watermark and recover the original image losslessly from the watermarked image. They have been applied to those sensitive fields, such as the medicine and the military. Since an embedding pixel value may exceed the limitation of pixel value during the embedding process, most of the reversible watermarking methods require a location-map to record those pixels for recovering cover images. Although the location-map can be compressed by a lossless compression algorithm, and then embed into the watermarked image, this lowers embedding capacity and increases the complexity of watermarking during the procedures of embedding and extraction. In this thesis, we propose a reversible location-map free of watermarking algorithm. This algorithm first exploits the sorting and the correlation of neighboring pixels to increase the embedding capacity. Next we find thresholds from the predicted values. If the predicted value of an embedding pixel is within the thresholds, we can ensure that the pixel has no underflow or overflow problem during embedding process. Therefore, we can recover the cover image without any distortion. The experimental results reveal that the performance of our proposed method outperforms that proposed by FUJIYOSHI et al. For example, the embedding capacity obtained by the proposed method is higher than that obtained by FUJIYOSHI et al. about 60%, and the PSNR of our scheme is higher than FUJIYOSHI et al. about 5 dB.

<p>To study engineering can be difficult, especially transforming theoretical knowledge into practice. To address this issue, Otto and Wood have developed a reverse engineering and redesign methodology, suggesting that it can be used as a tool in the process of learning mechanical engineering and design. The aim with this report is to</p><p>evaluate this statement, emphasizing on the reverse engineering process and evaluating its usefulness as an educational tool. In order to fully understand the process, two cordless screwdrivers will be reverse engineered, functioning as an example throughout the report. A theoretical background of the process will be</p><p>introduced, including descriptions concerning the different steps and their encompassed tools, tests and methods. Trough the implementation, the screwdrivers are disassembled, analysed and experienced, resulting in a clear product specification</p><p>with information of components and product functions. One example is the assembly plan, were the product structure is presented as two subassemblies with “layer on layer” assembly. Another result of the implementation is that the reverse engineering</p><p>process was experienced in reality, exposing the required modifications necessary in order to function as an educational tool. The main issue for the process is its focus on customer needs instead of product focus. Therefore, it is suggested that a new reverse</p><p>engineering process based on the existing one should be developed, focusing more on the product and less on the customer to better suit an educational purpose.</p>