Yes / Catalysts play a vital role in petroleum and chemical reactions. Intensified concerns for cleaner air with strict environmental regulations on sulfur content in addition to meet economic requirements have generated significant interests for the development of more efficient and innovative oxidative catalysts recently. In this study, a novel homemade nano catalyst (manganese oxide (MnO2) over tin (IV) oxide (SnO2)) was used for the first time as an effective catalyst in removing dibenzothiophene (DBT) from kerosene fuel using hydrogen peroxide (H2O2) as oxidant in catalytic oxidative-extractive desulfurization process (OEDS). The catalyst was prepared by impregnation method with various amount of MnO2 loaded on SnO2. The oxidation step was carried out at different operating parameters such as reaction temperature and reaction time in batch reactor. The extractive desulfurization step was performed by using acetonitrile as solvent under several operating conditions (agitation speed and mixing time). The activity of MnO2/SnO2 catalyst in removing various sulfur compounds from kerosene fuel at the best operating conditions was investigated in this work. The results of the catalyst characterization proved that a high dispersion of MnO2 over the SnO2 was obtained. The experiments showed that the highest DBT and various sulfur compounds removal efficiency from kerosene fuel under the best operating conditions (oxidation: 5% MnO2/SnO2, reaction temperature of 75 0C, and reaction time of 100 min, extraction: acetonitrile, agitation speed of 900 rpm, and mixing time of 30 min) via the catalytic oxidative-extractive desulfurization process was 92.4% and 91.2%, respectively. Also, the MnO2/SnO2 catalyst activity was studied after six consecutive oxidation cycles at the best operating conditions, and the catalyst prove satisfactory stability in terms of sulfur compounds removal. After that, the spent catalyst were regenerated by utilizing different solvents (methanol, ethanol and iso-octane), and the experimental data explained that iso-octane achieved highest regeneration efficiency. / This study was supported by College of Petroleum Processes Engineering, Tikrit University, Iraq and Ministry of Oil, Iraq.

No description available.

<p> Type IV secretion systems (T4SS) are essential for the virulence of many gram-negative pathogens. The systems studied here comprise eleven VirB proteins in case of Agrobacterium tumefaciens and twelve in case of Brucella suis. The VirB proteins associate in the cell envelope and form a complex that mediates the translocation of virulence factors into host cells. In this report, VirB8, a core component of T4SS, is characterized with regards to its interaction with itself and with other VirB proteins. </p> <p> VirB8 was found to exist in monomer-dimer equilibrium and the self-association was demonstrated by analytical ultracentrifugation, analytical gel filtration, surface plasmon resonance and bacterial two-hybrid assay. The above experiments demonstrated that residues M102, Y105 and E214 o fVirB8 from B. suis are involved in self-association and mutagenesis of these residues led to the impairment of T4SS function in B. suis. Furthermore, this information was utilized to unravel the contribution of VirB8 self-association towards T4SS assembly and function. To this end dimerization variants of VirB8 from Agrobacterium tumefaciens were created and the effects were assessed with purified proteins in vitro. Following this, the effects of VirB8 dimer site changes were assessed in vivo. Introduction of a cysteine residue at the predicted interface (V97C) supported DNA transfer but not T-pilus formation. Variants that reduced the self-association did not support T4SS functions and T-pilus formation. Moreover, VirB2- VirB5 co-fractionated with high molecular mass components from membranes of A. tumefaciens and VirB8 dimerization was shown to be necessary for VirB2 association with the high molecular mass components. Using purified VirB8 and VirB5 it was shown that VirB5 interacts with VirB8 via its globular domain and this interaction dissociates VirB8 dimers. Taking these results together, a mechanistic contribution of VirB8 dimerization to T4SS assembly was proposed. </p> <p> Next, the interactions of VirB8 with other core components (VirB9 and VirBlO) were analyzed by using various in vitro and in vivo experiments. Purified soluble periplasmic domains of VirB8, VirB9 and VirB10 were used in enzyme-linked immunosorbent assays, circular dichroism, and surface plasmon resonance experiments. The pair-wise interactions and self-association of VirB8, VirB9 and VirB 10 were demonstrated with the in vitro experiments. In addition, a ternary complex formation between VirB8, VirB9, and VirBlO was identified. Using the bacterial two-hybrid system, the dynamics of the interactions between VirB8-VirB9-VirB 10 full-length proteins were analyzed demonstrating that VirB9 stimulates VirB8 self-association, but that it inhibits the VirB10-VirB10 as well as the VirB8-VirB10 interaction. Based on these results, a dynamic model for secretion system assembly is proposed where VirB8 plays a role as an assembly factor that is not closely associated with the functional core complex comprising VirB9 and VirB10. </p> <p> The work reported in this thesis advances the understanding of VirB8 self-association and its contribution to T4SS assembly and function. Furthermore, the establishment of the bacterial two-hybrid system to detect VirB interactions has helped identify inhibitors for the VirB8 dimerization through collaboration with Dr. Athanasios Paschos. Moreover, techniques such as ELISA, analytical ultracentrifugation, circular dichroism and surface plasmon resonance will be utilized routinely to characterize other VirB-VirB interactions in future. </p> / Thesis / Doctor of Philosophy (PhD)

The following Thesis is comprised of two separate and individual parts, both of which relate to the disposal of hydrogen sulfide. Section One is an investigation into the possibility of developing a hydrogen sulfide decomposition process which would produce both hydrogen and elemental sulfur. Section Two deals with the speciation study of a catalyst used in a traditional process which converts hydrogen sulfide gas into elemental sulfur. / Section 1: <p> The disposal of hydrogen sulfide by electrolysis to produce both hydrogen and sulfur appears to an interesting alternative to the conventional Claus process which wastes the hydrogen content of hydrogen sulfide. The electrolysis at room temperature has been reported in the literature, however, the investigation was somewhat limited by the low conductivity displayed by the electrolysis solution (pyridine/hydrogen sulfide mixture). </p> <p> The primary goal of this research was to construct a suitable apparatus and carry out a series of conductivity measurements of liquid hydrogen sulfide at room temperature with and without the addition of possible electrolytes. The objective was to determine if an electrolyte could be found that would increase the conductivity to a suitably high level to warrant the further investigation of the electrolysis process. </p> <p> Of the six possible electrolytes, only tetrapropyl ammonium iodide increased the conductivity to a desirable level. A 0.4034 M solution of this alkyl ammonium iodide in liquid hydrogen sulfide increased the conductivity (at 23 C) from 7.00 X 10-8 ohm-1cm-1 for the pure solvent to 1.13 X 10-2 ohm-1cm-1. This increase was attributed to the formation of the corresponding hydrogen sulfide adduct and its subsequent dissociation in liquid hydrogen sulfide. </p> </p> Now that it has clearly been established that appropriately high conducting solutions of hydrogen sulfide can be prepared, the further investigation of the electrolysis of hydrogen sulfide as a viable industrial process is warranted. </p> Section 2: <p> This section deals with the investigation of species present in vanadium(IV): citrate solutions over a wide range of pH values. Various spectroscopic methods (UV/VIS, ESR, vanadium Sl FT-NMR) were used to probe this specific system. The accumulated spectroscopic data were rationalized on the basis of thirteen vanadium(IV) containing species, four of which were proposed to be vanadium(IV): citrate species. Based on the observed spectroscopic data an equilibrium diagram was prepared which illustrates the vanadium(IV) species present as a function of pH. </p> / Thesis / Master of Science (MSc)

Type IV pili (T4P) are protein filaments found on the surface of a variety of bacterial species and mediate biofilm formation, adhesion, and flagellum-independent twitching motility. The biogenesis of T4P is dependent on a cell envelope-spanning, multiprotein complex that localizes to the poles in rod-shaped cells. How these proteins localize and cross the peptidoglycan (PG) layer in the absence of dedicated PG-hydrolyzing enzymes is unknown. In P. aeruginosa, PilMNOP interact to form the alignment subcomplex, connected via PilP to PilQ, which forms the outer membrane secretin. We hypothesized that polar localization and integration of the T4P machinery was driven by ordered recruitment to future sites of cell division, placing assembly system components at division septa in the correct position before daughter-cell separation. To determine which T4P components are essential for localization of the complex, we fused the T4P inner membrane assembly protein PilO to the fluorescent protein mCherry to monitor its localization. mCherry-PilO localized to the cell poles and midcell in wild type bacteria. However, it was delocalized in a strain lacking PilQ. A PilQ-mCherry fusion localized to the cell poles, likely through its putative septal PG binding AmiN domains, suggesting that PilQ binds PG and thus localizes its partners to future sites of cell division. In the absence of the associated pilotin protein (PilF), which is required for PilQ multimerization in the OM, T4P components were polarly localized, implying that localization is not dependent on secretin formation. The results of this research support a pre-installation mechanism for integration of protein complexes in the gram negative cell envelope without PG hydrolysis, which may be applicable to other systems. / Thesis / Master of Science (MSc)

Yes

The Seleucid Empire expanded its territory to stretch from Thrace to India under the leadership of Antiochus III, making it one of the most expansive empires in the Hellenistic World. Antiochus III's subsequent loss at the Battle of Magnesia to Rome in 190 B.C. caused some of the satrapies of the empire to begin to rebel, and has led some historians to believe that the empire began an unrecoverable decline. In this investigation I will argue that the myth of decline in the post-Antiochus III era is invalid through analyzing the stability brought to the empire during the reign of his son, Antiochus IV. An investigation into Antiochus IV's stabilization of the Seleucid Empire has not been completed in English since 1966. Through analyzing his involvement in the southern and eastern regions of the Seleucid Empire as well as the internal reforms a clear picture of Antiochus IV's efforts towards stabilization becomes apparent.

No description available.

No description available.

Type IV pili (T4P) are long adhesive surface filaments produced by bacteria and are a key virulence factor for many pathogens. T4P are produced by a dynamic intracellular nanomachine that facilitates the assembly (extension) and disassembly (retraction) of pili. Pilus dynamics are enabled by the motor subcomplex of the nanomachine, where cytoplasmic ATPases power pilus assembly (PilB) and disassembly (PilT and PilU). In many, but not all, T4P expressing bacteria – including our model organism Pseudomonas aeruginosa – two retraction ATPases are required for functional retraction, which can be assessed by measuring twitching motility. Deletion of pilT results in loss of twitching and phage susceptibility (another hallmark of pilus function) while deletion of pilU results in loss of twitching but retention of phage susceptibility, indicating pili can still be retracted. We hypothesized that PilU adds to the force of pilus retraction, facilitating disassembly when the fiber is under tension. We mutated ΔpilU and pilU::Tn5 strains with ethyl methanesulfonate and screened for gain-of-twitching mutants. Whole genome sequencing revealed multiple point mutations in the major pilin protein PilA or the pilus adhesin, PilY1. These point mutations were recapitulated in a ΔpilU strain and restored twitching to varying degrees. Complementation of pilA point mutants with pilU in trans influenced the twitching zone of only one mutant, and in trans expression of wild-type pilA resulted in a significant reduction in twitching in most. The contribution of PilU to the force of pilus retraction was further investigated by a polyacrylamide micropillar assay, where no pulling events could be detected for either ΔpilT or ΔpilU mutants. Exopolysaccharide production, a proxy for surface sensing, was uncoupled from twitching motility in the pilA point mutants. These results are a significant step forward to understanding what PilU does and, provides insight to the dynamics of the pilus fiber. / Thesis / Master of Science (MSc) / Pseudomonas aeruginosa is a bacterium that causes serious infections. P. aeruginosa uses adhesive, “grappling hook” filaments called Type IV pili (T4P) to stick to its hosts. T4P can be repeatedly extended and retracted, allowing the bacteria to crawl on surfaces (twitching) but making them susceptible to bacteriophages, viruses that attach to pili then kill the bacterial cells. The motor proteins PilT and PilU are required for twitching, but only PilT is essential for phage killing, implying that pili are retracted even when PilU is missing. Here we hypothesized that PilU is important for twitching because it helps generate force for retraction when pili are under tension. We isolated multiple mutations in pilus components that restored twitching in the absence of PilU, and propose that these mutations allow for easier retraction of pili. This information helps us understand how T4P help the bacteria to spread during infection.