A series of sulfonate anionic lipids esters derived from 4-sulfobenzoic acid (single chain) or 5-sulfoisophthalic acid (double chain) with chain length from C14 to C18 were synthesized and characterized. The sodium salts were uniformly insoluble in ethanol; the tetramethylammonium salts of the single chain derivative from oleyl alcohol and the double chain derivative from 2-octyldodecan-1-ol were sufficiently soluble for subsequent experiments. Lipids in ethanol and aqueous buffers were mixed in a microfluidic system (NanoAssmblr ® microfluidic mixer) to prepare a lipid dispersion containing vesicles and/or nanoparticles. Initial studies on prediction and controlling vesicle size based on lipid geometric parameters showed that particle size could be successfully affected and controlled by altering lipid compositions consistent with the formation of vesicles. A survey using high resolution cryo-Scanning Transmission Electron microscopy of the sample made by the microfluidic mixer demonstrated that vesicles were formed but a majority of the sample reformed to other aggregates, which complicated the interpretation of the initial product distribution. Further investigation on the efficiency of incorporation of phospholipids into vesicles indicated that 55% of the initial phospholipid appeared in the vesicle fractions. Sulfonate anionic lipids are incorporated into vesicles with lower efficiency and reach a threshold beyond which the sulfonate lipid is not incorporated. Entrapment efficiency was studied with three dyes. Different concentrations of the hydrophobic neutral dye Nile red, the hydrophilic cationic dye neutral red and the hydrophilic anionic dye hydroxypyrene trisulfonate (HPTS) were prepared. The entrapment efficiency was quantitatively analyzed by HPLC, and electrospray mass spectrometry; up to 15% of the initial dye present could be entrapped. Vesicles permeability assays using the ion channel gramicidin and the ion carrier valinomycin with HPTS-loaded vesicle samples showed that vesicle samples made by the microfluidic mixer and made by a conventional extrusion method appeared to behave in the same manner. Addition of a sulfonate anionic lipid to the lipid mixture resulted in vesicle leakage. The unilamellar proportion of HPTS loaded vesicle samples was assessed using a mellitin assay. A vesicle sample made by the microfluidic mixer was 80% unilamellar; a vesicle sample made by the extrusion method on the same lipid mixture was 60% unilamellar. / Graduate / mengxiuzheng@gmail.com

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Studies directed toward the total synthesis of the cytotoxic steroidal alkaloid cortistatin A were carried out. In a model system, it was determined that a sequence of reactions involving a lithiocyclopropene addition-intramolecular [4 + 2] cycloaddition cascade and subsequent cyclopropylcarbinyl rearrangement allowed for ready access to the BCD rings of the core steroid. Implementation of this methodology en route to the fully functionalized natural product proved an effective means for the elaboration of the A ring carbocyclic framework. / text

published_or_final_version / Medicine / Master / Doctor of Medicine

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Several seismic properties of Lake Maracaibo are unique and difficult to understand. However, studies show that the two principal factors that affect the seismic data are likely to be the low compressional and shear wave velocities generated by the gassy sediment in the mud layer, and the high attenuation of the compressional and shear waves. This mud layer sediment is heavy and is not suspended in the water. Furthermore, it is compacted enough to support shear stresses and, therefore, has a finite shear wave velocity. In theory, the gas content of the sediment reduces the compressional wave velocity by an order of magnitude below the values for water saturated sediments, but in Lake Maracaibo several studies show that gassy sediment reduces the compressional wave velocity from 1500 m/s to between 300 m/s and 700 m/s. This situation produces high attenuation of the compressional waves that are traveling through the sediment in the first 100 m. However, the results of seismic modeling show that this velocity has to be between 700 m/s and 900 m/s in order to get reasonable results, at least in the study area. The results show that there are very important lithological differences between the zones with and without gassy sediments in the mud layer. The best match between the raw data and the synthetic seismogram was found when an embedded rigid shale layer was located within the mud layer, in the first 100 m. Unrealistic results were produced when the rigid shale layer was removed in the modeling. This rigid layer produces a destructive interference in the Stoneley wave that could be observed in the seismic data and the synthetic seismogram. In this research, the attenuation quality factor Q, an intrinsic property of rock, will be studied. Common attenuation mechanisms include grain sliding, viscous flow of pore fluid or gas, viscous relaxation and other features. Additionally, it will be shown that other factors can be proposed to account for the attenuation of compressional and shear waves in Lake Maracaibo sediments. They include: the viscous losses between the particles and the fluid immediately above the mud layer; and the solid friction losses between the particles, the mud layer and the gassy sediment. This research shows That the attenuation in the mud layer in the zone with gassy sediment is very different from the attenuation in the zone without gassy sediment, and that the compressional wave attenuation is larger in the mud layer zone with gassy sediment than in the mud layer zone without gassy sediment. Finally, the research shows that the ringing is an important phenomenon associated with the low velocity in the mud layer and that this ringing has more frequency content in the zone without gassy sediment than in the zone with gassy sediment.

Architectural research for Field-Programmable Gate Arrays (FPGAs) tends to use an experimental approach. The benchmark circuits are used not only to compare different architectures, but also to ensure that the FPGA is sufficiently flexible to implement the desired variety of circuits. The most common benchmark circuits used for architectural research are circuits from the Microelectronics Center of North Carolina (MCNC). These circuits are small; they occupy less than 3% [5] of the largest available commercial FPGA. Moreover, these circuits are more representative of the glue logic circuits that were targets of early devices. This contrasts with the trend towards implementing Systems on Chip (SoCs) on FPGAs where several functional modules are integrated into a single circuit which is mapped onto one device. In this thesis, we develop a synthetic system-level circuit generator that connects pre-existing circuits in a realistic manner to build large netlists that share the characteristics of real SoC circuits. This generator is based on a survey of contemporary circuit designs from industrial and academic sources. We demonstrate that these system-level circuits scale well and that their post-routing characteristics match the results of large pre-existing benchmarks better than the results of circuits from previous synthetic generators.

Despite many drawn parallels between carbon and phosphorus, the development of catena-phosphorus chemistry is superficially explored when compared to carbon. This lack of progression is especially highlighted for cationic phosphorus frameworks, as neutral and anionic phosphorus frameworks have been studied to a much greater extent. This stresses cationic catena-phosphorus frameworks as important molecules for an improved understanding of fundamental phosphorus chemistry. Recent advancements in synthetic methods demonstrate that phosphorus frameworks of this type are viable target molecules. Furthermore, the precedence of a variety of new cationic catena-phosphorus frameworks by such methods exemplify their versatility. Here, novel 1,3-diphosphino-2-phosphonium [R2P-PR2-PR2]+, 2-phosphino-1,3-diphosphonium [R3P-PR-PR3]+ and cyclo-triphosphinophosphonium [R2P(RP)3]+ cations have been isolated and characterized in order to study the insertion of phosphenium cations into the phosphorus-phosphorus bonds of catena-phosphines.

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