New tungsten ion source is produced by using single and double-pulse laser ablation system. Combi... more New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd:YAG laser beams (266+1064 nm) are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pu...
A level of the Nd:YAG oscillator stability has been experimentally determined for different setup... more A level of the Nd:YAG oscillator stability has been experimentally determined for different setups of resonator Q-switches. Performed experiments quantify an influence of an active modulation element on generated laser pulses stability. Different types of saturable absorbers were investigated and improved stability of double switching (active mode locker plus passive saturable absorber mode-locker) was confirmed. The best stability has been achieved with the aid of dual switching of an acousto-opticmodulator and a saturable absorber-dye solution 3955 in ethylalcohol to be used for satellite laser radar station at Helwan city in Egypt. The energy stability of the laser output can improve the accuracy and reliability of the satellite laser ranging station. The oscillator output picosecond pulses resulting from both the saturable absorber dye and three different multiple quantum well (semiconductor) saturable absorbers have been compared.Experimental results revealed that thedye ML51 m...
Environmental comparison between conventional and hybrid anaerobic baffled reactors (CABR and HAB... more Environmental comparison between conventional and hybrid anaerobic baffled reactors (CABR and HABR) was investigated. In the first study, the two reactors were operated, in parallel, from the same source of dairy wastewater at an organic loading rate of 3.33±0.03g-COD/L.d. The HABR was packed with sponge media characterized by specific surface area: 157 m 2 /m 3 , density: 65 kg/m 3 and voids ratio: 0.65. Results showed that, CABR and HABR achieved COD removal efficiencies of 72.50±2.40 and 87.86±2.12 % with biogas yield of 111.10±8.87 and 155.80±7.02 mL-CH 4 /g-COD r , respectively. The better methanogenic activity of HABR was attributed to the lower sludge yield (Y obs) of 0.067 g-VSS/g-COD (compared to Y obs of CABR: 0.084 g-VSS/g-COD). In the second investigation, experimental results were used to predict the greenhouse gas emissions (GHG) and economic performance of a large-scale ABR with a capacity of 200 m 3 /d. The CABR revealed lower GHG of 8.06±0.52 kg-CO 2 /m 3 than that ...
A Copper (Cu) target kept under partial vacuum conditions (10− 3 mbar) irradiated with focused fi... more A Copper (Cu) target kept under partial vacuum conditions (10− 3 mbar) irradiated with focused first-four harmonics of a Q-switched Nd:YAG laser radiation at wavelengths of 1064, 532, 355 and 266 nm with pulse duration 7, 6, 7 and 6 ns, respectively. The evaporated ions were detected at a distance of 40 mm away from the target, after having passed through the retarding mesh grid (Cu electrode). The laser radiation with peak intensity between 4.6×109 and 1.3×1011 W/cm2 creates a dense plasma having high ionization state. This paper presents generation and detection of highly stripped Cu ions and high current in laser produced plasma. The velocity distribution function of the plasma cloud which emitted from the Cu target flare is investigated by using a Faraday cup technique. The dependence of the current signals on various parameters, such as laser power, laser wavelengths and argon (Ar) pressure, is described. In general, a sharp increase in the plume current was observed as the voltage is increased and is related to arc formation.
8th International Conference on High-capacity Optical Networks and Emerging Technologies, 2011
ABSTRACT Nano structured metal oxides (WO3 and ZnO) were synthesized and impregnated with a noble... more ABSTRACT Nano structured metal oxides (WO3 and ZnO) were synthesized and impregnated with a noble metal palladium and it was found from the absorption spectra that the band gap energies of the palladium doped material revealed blue shifts compared to the band gap energies of their pure counterparts. Pure and doped material synthesized were used as a photo-catalyst in the presence of 355 nm UV laser radiation in the process of deactivation of Escherichia coli micro organism in water and it is observed that the doped material show a considerable enhancement of the deactivation process with higher bacteria decay rate constant and shorter depletion time, which is related to the widened band gap due to palladium doping.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
... The vacuum chamber gas pressure was measured using a Pirani gauge. It was noticed that the le... more ... The vacuum chamber gas pressure was measured using a Pirani gauge. It was noticed that the length, L, of the plasma produced under laser ablation increases with laser power. The discharge was maintained under an applied voltage of 375 V between the two electrodes. ...
Production of oil at pyrolysis of Ellajun oil shale was investigated at different heating rates (... more Production of oil at pyrolysis of Ellajun oil shale was investigated at different heating rates (0.2-2.8; 2.2-5.0 and 7.0-13.0 °C min-1 in a fixed-bed retort. Total weight loss and oil yield were calculated for the temperature range 610-873 K. Total weight loss of oil shale sample increased from 12.5% to 18% with increasing the heating rate from 0.2 to 13 °C min-1 , whereas shale oil yield (calculated based on Fisher Assay for Ellajun sample) decreased from 80% to 40%. Sulfur content of produced liquid hydrocarbons decreased from 7.4 wt.% to 6.5 wt.% with increasing heating rate and pyrolysis temperature. Density of the produced shale oil increased from 0.947 to 0.982 g cm-3 with increasing heating rate indicating the formation of heavier compounds. The rate of shale oil accumulation was monitored by digital mass scales. Higher heating rates resulted in higher rates of accumulation. The rate of oil and water collection passed through a maximum for different heating rates at different pyrolysis temperatures.
The 1,3-benzodioxol moiety present in safrole, apiole, and myristicin essential oils and benzodio... more The 1,3-benzodioxol moiety present in safrole, apiole, and myristicin essential oils and benzodioxol derivatives have shown a wide range of biological activities including antiepileptic, analgesic, antituberculosis, and antimicrobial potentials. Here, we have tested the antibacterial and antioxidant activities of a series of benzodioxol derivatives. Twelve compounds of aryl acetate and acetic acid benzodioxol were evaluated against different types of bacterial strains, including Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa using the broth dilution method, and the most potent compound was 3e, which exhibited the bacterial growth of with MICs of 125 (S. aureus), 250 (E. coli), 220 (E. faecalis), and 100 µg/mL (P. aeruginosa). Our positive control, cinoxacin, had MICs of 250 (S. aureus), 250 (E. coli), 250 (E. faecalis), and 500 µg/mL (P. aeruginosa). Antioxidant activity was evaluated for the synthesized compounds utilizing the DPPH assay. The 3a compound was the most active with an IC50 value of 21.44 µg/mL, while the IC50 values of compounds 3b, 3e, and 3f were 96.07, 58.45, and 72.17 µg/mL, respectively. In contrast, all compounds with the acetic acid functional group had weaker activity, with an IC50 range of 193.52–289.78 µg/mL compared with the potent antioxidant agent Trolox (IC50 = 1.93 µg/mL). In the present paper, new benzodioxol-based aryl acetate and acetic acid derivatives were evaluated for their antibacterial and antioxidant activities. The outcomes revealed that the antibacterial and antioxidant properties of some of the synthesized benzodioxol aryl acetate and acetic acid derivatives can be considered as valuable materials for the pharmaceutical industry. Thus, these molecules should be further evaluated in vivo as lead compounds for the discovery of new drug candidates.
During the fracture stimulation of oil and gas wells, fracturing fluids are used to create fractu... more During the fracture stimulation of oil and gas wells, fracturing fluids are used to create fractures and transport the proppant into the fractured reservoirs. The fracturing fluid viscosity is responsible for proppant suspension, the viscosity can be increased through the incorporation of guar polymer and cross-linkers. After the fracturing operation, the fluid viscosity is decreased by breakers for efficient oil and gas recovery. Different types of enzyme breakers have been engineered and employed to reduce the fracturing fluid′s viscosity, but thermal stability remains the major constraint for the use of enzymes. The latest enzyme engineering approaches such as direct evolution and rational design, have great potential to increase the enzyme breakers’ thermostability against high temperatures of reservoirs. In this review article, we have reviewed recently advanced enzyme molecular engineering technologies and how these strategies could be used to enhance the thermostability of en...
From ecological and industrial perspectives, Anoxybacillus flavithermus species that lives in a t... more From ecological and industrial perspectives, Anoxybacillus flavithermus species that lives in a thermophilic environment, are extremely important bacteria due to their potential in producing highly interesting compounds and enzymes. In order to understand the genetic makeup of these thermophiles, we have performed a comparative genomics study of 12 genome-sequenced strains of Anoxybacillus flavithermus bacteria. The genome size of Anoxybacillus flavithermus strains is from 2.5Mbp to 3.7Mbp and on average containing a low percentage of G + C genomic content (˜41.9%). We show that, on the basis of the total gene-content, Anoxybacillus flavithermus strains are grouped in three different subgroups. In the future, it would be interesting to explore these strain subgroups to further understand the lifestyle of thermophilic bacteria. Focussing on the Anoxybacillus flavithermus AK1 strain, which was isolated from a Hot Spring in Saudi Arabia and closely related to A. flavithermus NBRC strain, we identified a unique list of 75 genes specific to AK1 strain, of which 63 of them have homologs in other taxonomically related species. We speculate that these AK1-specific genes might be resulted due to horizontal gene transfer from other bacteria in order to adapt to the extreme environmental conditions. Moreover, we predicted three potential secondary metabolite gene clusters in the AK1 strain that further need to be experimentally characterised. Genomic annotation, secondary metabolite gene clusters and outcomes of the strain genomic comparisons from this study would be the basis for the strain-specific mathematical model for exploiting the metabolism for the industrial and ecological applications.
Todo esse trabalho de mestrado eu dedico a minha família, mas dedico especialmente aquela menina ... more Todo esse trabalho de mestrado eu dedico a minha família, mas dedico especialmente aquela menina que desde pequena sonhou ser professora, aquela que voltava da escola sonhando como seria as aulas que ela daria e que por motivos da vida teve esse sonho postergado, mas conseguiu atingi-lo. Essa menina que se tornou mulher e posteriormente mãe, uma mãe em todo o sentido da palavra, que perdeu noites de sono olhando seu filho na doença, que trocou muitas fraldas e limpou alguns vômitos, tem um amor em seu coração que não da para medir, que viu seu menino partir em busca de um futuro, sofrendo com sua ausência, saiba que ele também sofreu em silêncio. Essa mulher que sempre deu maior força a seu menino e por mais bobas que fossem suas conquitas, sempre se sentia toda orgulhosa. Enfim, aquela que tanto queria ser professora, hoje seu filho também se torna um professor... hoje ele volta para casa... MUITO obrigado por tudo, de verdade... Amo você!! V Agradecimentos O meu primeiro e mais importante agradecimento de meu coração é a Deus... minha vida tomou rumo que não imaginava e Deus me conduz a cada curva dessa estrada. Agradeço a Ele, pois tudo que fiz até esse momento, se não fosse por Sua força não teria acontecido. Agradeço em segundo lugar a minha mãe Gleucione, pai Luiz Assis e irmã Maria Leíza, os quais me ajudaram de forma ininterrupta ao longo dessa caminhada, sempre com MUITO carinho e amor. Agradeço por compreenderem os meus momentos de ausência e falta de paciência. Obrigado a Edielly, minha namorada, que me deu muita força, em especial ao longo do primeiro ano. Agradeço aos colegas da pós-graduação Caio, Marcos, Lucas que de certa forma sempre se fizeram presentes. Agradeço ainda aqueles amigos de mestrado Roberta que tantos domingos me ajudou em meus experimentos, Vinicius que se tornou um grande parceiro e que sempre se colocou a disposição para me auxiliar. Aline, ahh Aline, MUITO obrigado por tudo, sem você, com certeza a estrada teria sido bem mais difícil. Agradeço ainda ao João Paulo, que NUNCA negou ajuda em qualquer momento. Sem vocês, com certeza tudo seria mais difícil. Não há como deixar de agradecer a Ângela que sempre se dispôs a ajudar, cortando os casos necessários. Lúbia, muito obrigado pelos conselhos e ajuda a cada momento. Adalci, sempre com paciência, e disposição ao auxílio. Novamente, sem vocês, tudo teria sido bem mais difícil. Agradeço aos amigos da graduação que sempre se dispuseram a ajudar, obrigado Maria Cecília, Ludiel, Anaíra, dentre muitos outros... Por último e não menos importante, agradeço de coração aos professores Sérgio Vitorino, Paulo Rogério, João César e Gabriela, os quais sempre se dispuseram a ajudar de alguma forma. Muito obrigado a todos! Agradeço ainda, para aquele que sempre fui um admirador e hoje tenho o prazer de podê-lo chama-lo de amigo, professor Adriano, obrigado! Um grande e forte abraço! VI "Se Deus é por nós, quems erá contra nós..." (Rm 8:31) "Assim é, se lhe parece" (Pirandello) VII SUMÁRIO LISTA DE ABREVIATURAS.
This preliminary study tracks the response of living benthic foraminifera at a polluted site in e... more This preliminary study tracks the response of living benthic foraminifera at a polluted site in eastern Bahrain, with the aim to determine the effects of recent anthropogenic pollution on their distribution patterns and morphological deformities. The boat harbor in Askar, Bahrain is subjected to pollution by nutrients, organic matter, and hydrocarbons. Foraminiferal density is found to be higher at the polluted site compared with a nearby unpolluted site, suggesting a possible higher amount of available nutrients for the benthic foraminifera. Seven taxonomical groups were recognized in the polluted transect, including Ammonia, Glabratellina, Murrayinella, Elphidium, Brizalina, miliolids, and peneroplids. By comparing the foraminiferal assemblages with a nearby unpolluted transect, the genus Murrayinella appeared to be a dominant and pervasive taxon, as it was able to proliferate in the organically polluted environment. The results are contradictory to previously published findings on modern foraminiferal assemblages in the Arabian Gulf, as Murrayinella is rarely reported. However, the population of miliolids was drastically reduced at the polluted site due to high organic matter pollution, which might support the sensitive nature of this taxonomic group. In any case, the miliolids can be considered as a pollution proxy for future biomonitoring studies in the region.
Abstract A novel approach was used to synthesize a silver doped-CNT membrane, with the aim of ful... more Abstract A novel approach was used to synthesize a silver doped-CNT membrane, with the aim of fully utilizing the anti-toxic properties of CNTs and silver. No binder was used for the synthesis of the membrane; instead, silver particles served as a binding material for the CNTs after sintering at high temperature. In the first step, CNTs were impregnated with different loadings of silver (1, 10 and 20 wt.%) via a wet chemistry technique. Impregnated CNTs were then compacted at 200 MPa and sintered at 800 °C for 3 h to form a compact disk (membrane). The powder materials were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and thermogravimetric analysis, while the membranes were characterized by measuring their porosity, contact angle, diametrical compression test, pure water permeate flux and antibacterial properties. The affinity of the membranes to biofouling was studied using Escherichia coli (E. coli). The produced membrane showed a high water permeate flux and exhibited strong antibacterial properties. All of the membranes with different silver loadings were able to remove/kill 100% of the bacteria tested; however, the CNT membrane with 10% silver showed a superior performance to the others. All bacteria were removed/killed by the membrane with 10% silver loading after the suspension had passed for only 60 min. These membranes would be advantageous in a continuous filtration system for the removal of different contaminants from water via desalination, adsorption and sieving.
Nanostructured ZnO photo catalyst was synthesized by precipitation method and was applied in conj... more Nanostructured ZnO photo catalyst was synthesized by precipitation method and was applied in conjunction with 355 nm pulsed laser irradiation for effective disinfection of the water contaminated with Escherichia coli micro organism. The morphological studies using X-Ray Diffractometer (XRD) and Transmission Electron Microscope (TEM) were carried out on the synthesized nano-ZnO, and these studies indicated that the catalyst has the crystallographic structure of hexagonal wurtzite and has the grain size of around 20-40 nm. The bacteria decay rate constants were estimated for nine different concentrations of nano-ZnO in infected water. The parametric optimization was carried out, and we could reach the decay rate constant as high as 0.24 min ,-1 which is higher than micro-structured ZnO and the familiar TiO 2 photo catalysts under similar experimental condition.
New tungsten ion source is produced by using single and double-pulse laser ablation system. Combi... more New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd:YAG laser beams (266+1064 nm) are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pu...
A level of the Nd:YAG oscillator stability has been experimentally determined for different setup... more A level of the Nd:YAG oscillator stability has been experimentally determined for different setups of resonator Q-switches. Performed experiments quantify an influence of an active modulation element on generated laser pulses stability. Different types of saturable absorbers were investigated and improved stability of double switching (active mode locker plus passive saturable absorber mode-locker) was confirmed. The best stability has been achieved with the aid of dual switching of an acousto-opticmodulator and a saturable absorber-dye solution 3955 in ethylalcohol to be used for satellite laser radar station at Helwan city in Egypt. The energy stability of the laser output can improve the accuracy and reliability of the satellite laser ranging station. The oscillator output picosecond pulses resulting from both the saturable absorber dye and three different multiple quantum well (semiconductor) saturable absorbers have been compared.Experimental results revealed that thedye ML51 m...
Environmental comparison between conventional and hybrid anaerobic baffled reactors (CABR and HAB... more Environmental comparison between conventional and hybrid anaerobic baffled reactors (CABR and HABR) was investigated. In the first study, the two reactors were operated, in parallel, from the same source of dairy wastewater at an organic loading rate of 3.33±0.03g-COD/L.d. The HABR was packed with sponge media characterized by specific surface area: 157 m 2 /m 3 , density: 65 kg/m 3 and voids ratio: 0.65. Results showed that, CABR and HABR achieved COD removal efficiencies of 72.50±2.40 and 87.86±2.12 % with biogas yield of 111.10±8.87 and 155.80±7.02 mL-CH 4 /g-COD r , respectively. The better methanogenic activity of HABR was attributed to the lower sludge yield (Y obs) of 0.067 g-VSS/g-COD (compared to Y obs of CABR: 0.084 g-VSS/g-COD). In the second investigation, experimental results were used to predict the greenhouse gas emissions (GHG) and economic performance of a large-scale ABR with a capacity of 200 m 3 /d. The CABR revealed lower GHG of 8.06±0.52 kg-CO 2 /m 3 than that ...
A Copper (Cu) target kept under partial vacuum conditions (10− 3 mbar) irradiated with focused fi... more A Copper (Cu) target kept under partial vacuum conditions (10− 3 mbar) irradiated with focused first-four harmonics of a Q-switched Nd:YAG laser radiation at wavelengths of 1064, 532, 355 and 266 nm with pulse duration 7, 6, 7 and 6 ns, respectively. The evaporated ions were detected at a distance of 40 mm away from the target, after having passed through the retarding mesh grid (Cu electrode). The laser radiation with peak intensity between 4.6×109 and 1.3×1011 W/cm2 creates a dense plasma having high ionization state. This paper presents generation and detection of highly stripped Cu ions and high current in laser produced plasma. The velocity distribution function of the plasma cloud which emitted from the Cu target flare is investigated by using a Faraday cup technique. The dependence of the current signals on various parameters, such as laser power, laser wavelengths and argon (Ar) pressure, is described. In general, a sharp increase in the plume current was observed as the voltage is increased and is related to arc formation.
8th International Conference on High-capacity Optical Networks and Emerging Technologies, 2011
ABSTRACT Nano structured metal oxides (WO3 and ZnO) were synthesized and impregnated with a noble... more ABSTRACT Nano structured metal oxides (WO3 and ZnO) were synthesized and impregnated with a noble metal palladium and it was found from the absorption spectra that the band gap energies of the palladium doped material revealed blue shifts compared to the band gap energies of their pure counterparts. Pure and doped material synthesized were used as a photo-catalyst in the presence of 355 nm UV laser radiation in the process of deactivation of Escherichia coli micro organism in water and it is observed that the doped material show a considerable enhancement of the deactivation process with higher bacteria decay rate constant and shorter depletion time, which is related to the widened band gap due to palladium doping.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
... The vacuum chamber gas pressure was measured using a Pirani gauge. It was noticed that the le... more ... The vacuum chamber gas pressure was measured using a Pirani gauge. It was noticed that the length, L, of the plasma produced under laser ablation increases with laser power. The discharge was maintained under an applied voltage of 375 V between the two electrodes. ...
Production of oil at pyrolysis of Ellajun oil shale was investigated at different heating rates (... more Production of oil at pyrolysis of Ellajun oil shale was investigated at different heating rates (0.2-2.8; 2.2-5.0 and 7.0-13.0 °C min-1 in a fixed-bed retort. Total weight loss and oil yield were calculated for the temperature range 610-873 K. Total weight loss of oil shale sample increased from 12.5% to 18% with increasing the heating rate from 0.2 to 13 °C min-1 , whereas shale oil yield (calculated based on Fisher Assay for Ellajun sample) decreased from 80% to 40%. Sulfur content of produced liquid hydrocarbons decreased from 7.4 wt.% to 6.5 wt.% with increasing heating rate and pyrolysis temperature. Density of the produced shale oil increased from 0.947 to 0.982 g cm-3 with increasing heating rate indicating the formation of heavier compounds. The rate of shale oil accumulation was monitored by digital mass scales. Higher heating rates resulted in higher rates of accumulation. The rate of oil and water collection passed through a maximum for different heating rates at different pyrolysis temperatures.
The 1,3-benzodioxol moiety present in safrole, apiole, and myristicin essential oils and benzodio... more The 1,3-benzodioxol moiety present in safrole, apiole, and myristicin essential oils and benzodioxol derivatives have shown a wide range of biological activities including antiepileptic, analgesic, antituberculosis, and antimicrobial potentials. Here, we have tested the antibacterial and antioxidant activities of a series of benzodioxol derivatives. Twelve compounds of aryl acetate and acetic acid benzodioxol were evaluated against different types of bacterial strains, including Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa using the broth dilution method, and the most potent compound was 3e, which exhibited the bacterial growth of with MICs of 125 (S. aureus), 250 (E. coli), 220 (E. faecalis), and 100 µg/mL (P. aeruginosa). Our positive control, cinoxacin, had MICs of 250 (S. aureus), 250 (E. coli), 250 (E. faecalis), and 500 µg/mL (P. aeruginosa). Antioxidant activity was evaluated for the synthesized compounds utilizing the DPPH assay. The 3a compound was the most active with an IC50 value of 21.44 µg/mL, while the IC50 values of compounds 3b, 3e, and 3f were 96.07, 58.45, and 72.17 µg/mL, respectively. In contrast, all compounds with the acetic acid functional group had weaker activity, with an IC50 range of 193.52–289.78 µg/mL compared with the potent antioxidant agent Trolox (IC50 = 1.93 µg/mL). In the present paper, new benzodioxol-based aryl acetate and acetic acid derivatives were evaluated for their antibacterial and antioxidant activities. The outcomes revealed that the antibacterial and antioxidant properties of some of the synthesized benzodioxol aryl acetate and acetic acid derivatives can be considered as valuable materials for the pharmaceutical industry. Thus, these molecules should be further evaluated in vivo as lead compounds for the discovery of new drug candidates.
During the fracture stimulation of oil and gas wells, fracturing fluids are used to create fractu... more During the fracture stimulation of oil and gas wells, fracturing fluids are used to create fractures and transport the proppant into the fractured reservoirs. The fracturing fluid viscosity is responsible for proppant suspension, the viscosity can be increased through the incorporation of guar polymer and cross-linkers. After the fracturing operation, the fluid viscosity is decreased by breakers for efficient oil and gas recovery. Different types of enzyme breakers have been engineered and employed to reduce the fracturing fluid′s viscosity, but thermal stability remains the major constraint for the use of enzymes. The latest enzyme engineering approaches such as direct evolution and rational design, have great potential to increase the enzyme breakers’ thermostability against high temperatures of reservoirs. In this review article, we have reviewed recently advanced enzyme molecular engineering technologies and how these strategies could be used to enhance the thermostability of en...
From ecological and industrial perspectives, Anoxybacillus flavithermus species that lives in a t... more From ecological and industrial perspectives, Anoxybacillus flavithermus species that lives in a thermophilic environment, are extremely important bacteria due to their potential in producing highly interesting compounds and enzymes. In order to understand the genetic makeup of these thermophiles, we have performed a comparative genomics study of 12 genome-sequenced strains of Anoxybacillus flavithermus bacteria. The genome size of Anoxybacillus flavithermus strains is from 2.5Mbp to 3.7Mbp and on average containing a low percentage of G + C genomic content (˜41.9%). We show that, on the basis of the total gene-content, Anoxybacillus flavithermus strains are grouped in three different subgroups. In the future, it would be interesting to explore these strain subgroups to further understand the lifestyle of thermophilic bacteria. Focussing on the Anoxybacillus flavithermus AK1 strain, which was isolated from a Hot Spring in Saudi Arabia and closely related to A. flavithermus NBRC strain, we identified a unique list of 75 genes specific to AK1 strain, of which 63 of them have homologs in other taxonomically related species. We speculate that these AK1-specific genes might be resulted due to horizontal gene transfer from other bacteria in order to adapt to the extreme environmental conditions. Moreover, we predicted three potential secondary metabolite gene clusters in the AK1 strain that further need to be experimentally characterised. Genomic annotation, secondary metabolite gene clusters and outcomes of the strain genomic comparisons from this study would be the basis for the strain-specific mathematical model for exploiting the metabolism for the industrial and ecological applications.
Todo esse trabalho de mestrado eu dedico a minha família, mas dedico especialmente aquela menina ... more Todo esse trabalho de mestrado eu dedico a minha família, mas dedico especialmente aquela menina que desde pequena sonhou ser professora, aquela que voltava da escola sonhando como seria as aulas que ela daria e que por motivos da vida teve esse sonho postergado, mas conseguiu atingi-lo. Essa menina que se tornou mulher e posteriormente mãe, uma mãe em todo o sentido da palavra, que perdeu noites de sono olhando seu filho na doença, que trocou muitas fraldas e limpou alguns vômitos, tem um amor em seu coração que não da para medir, que viu seu menino partir em busca de um futuro, sofrendo com sua ausência, saiba que ele também sofreu em silêncio. Essa mulher que sempre deu maior força a seu menino e por mais bobas que fossem suas conquitas, sempre se sentia toda orgulhosa. Enfim, aquela que tanto queria ser professora, hoje seu filho também se torna um professor... hoje ele volta para casa... MUITO obrigado por tudo, de verdade... Amo você!! V Agradecimentos O meu primeiro e mais importante agradecimento de meu coração é a Deus... minha vida tomou rumo que não imaginava e Deus me conduz a cada curva dessa estrada. Agradeço a Ele, pois tudo que fiz até esse momento, se não fosse por Sua força não teria acontecido. Agradeço em segundo lugar a minha mãe Gleucione, pai Luiz Assis e irmã Maria Leíza, os quais me ajudaram de forma ininterrupta ao longo dessa caminhada, sempre com MUITO carinho e amor. Agradeço por compreenderem os meus momentos de ausência e falta de paciência. Obrigado a Edielly, minha namorada, que me deu muita força, em especial ao longo do primeiro ano. Agradeço aos colegas da pós-graduação Caio, Marcos, Lucas que de certa forma sempre se fizeram presentes. Agradeço ainda aqueles amigos de mestrado Roberta que tantos domingos me ajudou em meus experimentos, Vinicius que se tornou um grande parceiro e que sempre se colocou a disposição para me auxiliar. Aline, ahh Aline, MUITO obrigado por tudo, sem você, com certeza a estrada teria sido bem mais difícil. Agradeço ainda ao João Paulo, que NUNCA negou ajuda em qualquer momento. Sem vocês, com certeza tudo seria mais difícil. Não há como deixar de agradecer a Ângela que sempre se dispôs a ajudar, cortando os casos necessários. Lúbia, muito obrigado pelos conselhos e ajuda a cada momento. Adalci, sempre com paciência, e disposição ao auxílio. Novamente, sem vocês, tudo teria sido bem mais difícil. Agradeço aos amigos da graduação que sempre se dispuseram a ajudar, obrigado Maria Cecília, Ludiel, Anaíra, dentre muitos outros... Por último e não menos importante, agradeço de coração aos professores Sérgio Vitorino, Paulo Rogério, João César e Gabriela, os quais sempre se dispuseram a ajudar de alguma forma. Muito obrigado a todos! Agradeço ainda, para aquele que sempre fui um admirador e hoje tenho o prazer de podê-lo chama-lo de amigo, professor Adriano, obrigado! Um grande e forte abraço! VI "Se Deus é por nós, quems erá contra nós..." (Rm 8:31) "Assim é, se lhe parece" (Pirandello) VII SUMÁRIO LISTA DE ABREVIATURAS.
This preliminary study tracks the response of living benthic foraminifera at a polluted site in e... more This preliminary study tracks the response of living benthic foraminifera at a polluted site in eastern Bahrain, with the aim to determine the effects of recent anthropogenic pollution on their distribution patterns and morphological deformities. The boat harbor in Askar, Bahrain is subjected to pollution by nutrients, organic matter, and hydrocarbons. Foraminiferal density is found to be higher at the polluted site compared with a nearby unpolluted site, suggesting a possible higher amount of available nutrients for the benthic foraminifera. Seven taxonomical groups were recognized in the polluted transect, including Ammonia, Glabratellina, Murrayinella, Elphidium, Brizalina, miliolids, and peneroplids. By comparing the foraminiferal assemblages with a nearby unpolluted transect, the genus Murrayinella appeared to be a dominant and pervasive taxon, as it was able to proliferate in the organically polluted environment. The results are contradictory to previously published findings on modern foraminiferal assemblages in the Arabian Gulf, as Murrayinella is rarely reported. However, the population of miliolids was drastically reduced at the polluted site due to high organic matter pollution, which might support the sensitive nature of this taxonomic group. In any case, the miliolids can be considered as a pollution proxy for future biomonitoring studies in the region.
Abstract A novel approach was used to synthesize a silver doped-CNT membrane, with the aim of ful... more Abstract A novel approach was used to synthesize a silver doped-CNT membrane, with the aim of fully utilizing the anti-toxic properties of CNTs and silver. No binder was used for the synthesis of the membrane; instead, silver particles served as a binding material for the CNTs after sintering at high temperature. In the first step, CNTs were impregnated with different loadings of silver (1, 10 and 20 wt.%) via a wet chemistry technique. Impregnated CNTs were then compacted at 200 MPa and sintered at 800 °C for 3 h to form a compact disk (membrane). The powder materials were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and thermogravimetric analysis, while the membranes were characterized by measuring their porosity, contact angle, diametrical compression test, pure water permeate flux and antibacterial properties. The affinity of the membranes to biofouling was studied using Escherichia coli (E. coli). The produced membrane showed a high water permeate flux and exhibited strong antibacterial properties. All of the membranes with different silver loadings were able to remove/kill 100% of the bacteria tested; however, the CNT membrane with 10% silver showed a superior performance to the others. All bacteria were removed/killed by the membrane with 10% silver loading after the suspension had passed for only 60 min. These membranes would be advantageous in a continuous filtration system for the removal of different contaminants from water via desalination, adsorption and sieving.
Nanostructured ZnO photo catalyst was synthesized by precipitation method and was applied in conj... more Nanostructured ZnO photo catalyst was synthesized by precipitation method and was applied in conjunction with 355 nm pulsed laser irradiation for effective disinfection of the water contaminated with Escherichia coli micro organism. The morphological studies using X-Ray Diffractometer (XRD) and Transmission Electron Microscope (TEM) were carried out on the synthesized nano-ZnO, and these studies indicated that the catalyst has the crystallographic structure of hexagonal wurtzite and has the grain size of around 20-40 nm. The bacteria decay rate constants were estimated for nine different concentrations of nano-ZnO in infected water. The parametric optimization was carried out, and we could reach the decay rate constant as high as 0.24 min ,-1 which is higher than micro-structured ZnO and the familiar TiO 2 photo catalysts under similar experimental condition.
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Papers by Amjad Khalil