Showing papers by "King Fahd University of Petroleum and Minerals published in 2011"

Germline BAP1 mutations predispose to malignant mesothelioma

Abstract: Because only a small fraction of asbestos-exposed individuals develop malignant mesothelioma, and because mesothelioma clustering is observed in some families, we searched for genetic predisposing factors. We discovered germline mutations in the gene encoding BRCA1 associated protein-1 (BAP1) in two families with a high incidence of mesothelioma, and we observed somatic alterations affecting BAP1 in familial mesotheliomas, indicating biallelic inactivation. In addition to mesothelioma, some BAP1 mutation carriers developed uveal melanoma. We also found germline BAP1 mutations in 2 of 26 sporadic mesotheliomas; both individuals with mutant BAP1 were previously diagnosed with uveal melanoma. We also observed somatic truncating BAP1 mutations and aberrant BAP1 expression in sporadic mesotheliomas without germline mutations. These results identify a BAP1-related cancer syndrome that is characterized by mesothelioma and uveal melanoma. We hypothesize that other cancers may also be involved and that mesothelioma predominates upon asbestos exposure. These findings will help to identify individuals at high risk of mesothelioma who could be targeted for early intervention.

Rice Husk and Its Ash as Low-Cost Adsorbents in Water and Wastewater Treatment

Abstract: Rice husk, which is a relatively abundant and inexpensive material, is currently being investigated as an adsorbent for the removal of various pollutants from water and wastewaters. Various pollutants, such as dyes, phenols, organic compounds, pesticides, inorganic anions, and heavy metals can be removed very effectively with rice husk as an adsorbent. This article presents a brief review on the role of rice husk and rice husk ash in the removal of various pollutants from wastewater. Studies on the adsorption of various pollutants by rice husk materials are reviewed and the adsorption mechanism, influencing factors, favorable conditions, etc., discussed in this article. It is evident from the review that rice husk and its ash can be potentially utilized for the removal of various pollutants from water and wastewaters.

Noise spectroscopy through dynamical decoupling with a superconducting flux qubit

Abstract: Quantum coherence in natural and artificial spin systems is fundamental to applications ranging from quantum information science to magnetic-resonance imaging and identification. Several multipulse control sequences targeting generalized noise models have been developed to extend coherence by dynamically decoupling a spin system from its noisy environment. In any particular implementation, however, the efficacy of these methods is sensitive to the specific frequency distribution of the noise, suggesting that these same pulse sequences could also be used to probe the noise spectrum directly. Here we demonstrate noise spectroscopy by means of dynamical decoupling using a superconducting qubit with energy-relaxation time T1 =12 μs. We first demonstrate that dynamical decoupling improves the coherence time T 2 in this system up to the T2 =2 T1 limit (pure dephasing times exceeding 100 μs), and then leverage its filtering properties to probe the environmental noise over a frequency (f) range 0.2-20 MHz, observing a 1/fα distribution with α < 1. The characterization of environmental noise has broad utility for spin-resonance applications, enabling the design of optimized coherent-control methods, promoting device and materials engineering, and generally improving coherence. © 2011 Macmillan Publishers Limited. All rights reserved.

Nanostructured materials for water desalination.

Abstract: Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity.

Electrochemical Analysis of Some Toxic Metals by Ion–Selective Electrodes

Abstract: An overview of potentiometric sensors that are capable of detecting toxic heavy metal ions in environmental samples is presented and discussed. Notwithstanding the tremendous work performed so far,...

A New Formula for the BER of Binary Modulations with Dual-Branch Selection over Generalized-K

Abstract: Error performance is one of the main performance measures and the derivation of its closed-form expression has proved to be quite involved for certain communication systems operating over composite fading channels. In this letter, a unified closed-form expression, applicable to different binary modulation schemes, for the bit error rate of dual-branch selection diversity based systems undergoing independent but not necessarily identically distributed generalized-K fading is derived in terms of the extended generalized bivariate Meijer G-function.

Synthesis of MWCNT/MnO2 and their application for simultaneous oxidation of arsenite and sorption of arsenate

Abstract: It is well known that arsenite [As(III)] is less effectively removed than arsenate [As(V)] by most treatment technologies Thus, pre-oxidation of As(III) to As(V) is required prior to adsorption Here, the oxidation properties of manganese oxides with adsorption features of multiwall carbon nanotubes (MWCNTs) have been combined in a composite of MWCNT/MnO2 The composite was characterized by Fourier transform infrared absorption spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and energy dispersive X-ray (EDX) and X-ray diffraction (XRD) In batch culture experiments, MWCNTs and the MWCNT/MnO2 composite were examined for As(III) and As(V) The results reveal that MnO2 in the composite plays a key role in enhancing As(III) removal and As(III) removal is not as effective as As(V) removal for MWCNTs The retention of arsenite and arsenate is slightly pH dependent The reported composite can be regenerated as it was confirmed by SEM and EDX analysis The study could be considered as a model of preparation and investigation of a multifunctional material that can be used in wastewater treatment for removal of arsenic

Optimal Design of Microgrids in Autonomous and Grid-Connected Modes Using Particle Swarm Optimization

Abstract: The dynamic nature of the distribution network challenges the stability and control effectiveness of the microgrids in both grid-connected and autonomous modes. In this paper, linear and nonlinear models of microgrids operating in different modes are presented. Optimal design of LC filter, controller parameters, and damping resistance is carried out in case of grid-connected mode. On the other hand, controller parameters and power sharing coefficients are optimized in case of autonomous mode. The control problem has been formulated as an optimization problem where particle swarm optimization is employed to search for optimal settings of the optimized parameters in each mode. In addition, nonlinear time-domain-based as well as eigenvalue-based objective functions are proposed to minimize the error in the measured power and to enhance the damping characteristics, respectively. Finally, the nonlinear time-domain simulation has been carried out to assess the effectiveness of the proposed controllers under different disturbances and loading conditions. The results show satisfactory performance with efficient damping characteristics of the microgrid considered in this study. Additionally, the effectiveness of the proposed approach for optimizing different parameters and its robustness have been confirmed through the eigenvalue analysis and nonlinear time-domain simulations.

Entropy Generation Analysis of Desalination Technologies

Abstract: Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on the required energy input. When defining Second Law efficiency, the useful exergy output of the system must be properly defined. For desalination systems, this is the minimum least work of separation required to extract a unit of water from a feed stream of a given salinity. In order to evaluate the Second Law efficiency, entropy generation mechanisms present in a wide range of desalination processes are analyzed. In particular, entropy generated in the run down to equilibrium of discharge streams must be considered. Physical models are applied to estimate the magnitude of entropy generation by component and individual processes. These formulations are applied to calculate the total entropy generation in several desalination systems including multiple effect distillation, multistage flash, membrane distillation, mechanical vapor compression, reverse osmosis, and humidification-dehumidification. Within each technology, the relative importance of each source of entropy generation is discussed in order to determine which should be the target of entropy generation minimization. As given here, the correct application of Second Law efficiency shows which systems operate closest to the reversible limit and helps to indicate which systems have the greatest potential for improvement.

Nano ZnO synthesis by modified sol gel method and its application in heterogeneous photocatalytic removal of phenol from water

Abstract: Zinc oxide nanoparticles were synthesized by precipitation and modified sol gel methods. The influence of calcination temperature on morphology and crystallite size of ZnO was studied by varying temperature from 400 to 700 °C. The nano-structured ZnO particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDXS) and tranmission electron microscopy (TEM). The photo catalytic activity of as-prepared ZnO was evaluated by degradation of phenol under UV laser irradiation. The Photocatalytic degradation (PCD) efficiency of ZnO was found to decrease with the increase in calcination temperature due to agglomeration of particles and the increase in particle size. In addition to the effect of calcination temperature, the influence of various other parameters such as photocatalyst concentration, initial pH and the initial phenol concentration was also investigated to achieve the maximum PCD of phenol. The operational parameters show the expected influence regarding the efficiency of the photocatalytic degradation process. The results follow the pseudo-first order rate kinetics.

High-pressure and high-temperature characteristics of a Fabry―Perot interferometer based on photonic crystal fiber

Abstract: A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber. The photonic crystal fiber functions as a Fabry-Perot cavity and serves as a direct sensing probe without any additional components. Its pressure and temperature responses in the range of 0-40 MPa and 25°C-700°C were experimentally studied. The proposed sensor is easy to fabricate, potentially low-cost, and compact in size, which makes it very attractive for high-pressure and high-temperature sensing applications.

Primary Alcohols from Terminal Olefins: Formal Anti-Markovnikov Hydration via Triple Relay Catalysis

Abstract: Alcohol synthesis is critical to the chemical and pharmaceutical industries. The addition of water across olefins to form primary alcohols (anti-Markovnikov olefin hydration) would be a broadly useful reaction but has largely proven elusive; an indirect hydroboration/oxidation sequence requiring stoichiometric borane and oxidant is currently the most practical methodology. Here, we report a more direct approach with the use of a triple relay catalysis system that couples palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction cycles. Aryl-substituted terminal olefins are converted to primary alcohols by net reaction with water in good yield and excellent regioselectivity.

Barriers in the selection of offshore software development outsourcing vendors: An exploratory study using a systematic literature review

Abstract: Context: Software development outsourcing is a contract-based relationship between client and vendor organisations in which a client contracts out all or part of its software development activities to a vendor, who provides agreed services for remuneration. Objective: The objective is to identify various barriers that have a negative impact on software outsourcing clients in the selection process of offshore software development outsourcing vendors. Method: We have performed a systematic literature review (SLR) process for the identification of barriers. We have performed all the SLR steps such as the protocol development, initial selection, final selection, quality assessment, data extraction and data synthesis. Results: We have identified barriers such as 'language and cultural barriers', 'country instability', 'lack of project management', 'lack of protection for intellectual property rights' and 'lack of technical capability' that generally have a negative impact on outsourcing clients. We have identified only one common frequently cited barrier in three types of organisations (i.e. small, medium and large) which is 'language and cultural barriers'. We did not identify any common frequently cited barrier in three continents (Asia, North America and Europe) and in two decades (1990-1999 and 2000-mid 2008). The results also reveal the similarities and differences in the barriers identified through different study strategies. Conclusions: Vendors should address frequently cited barriers such as 'language and cultural barriers', 'country instability', 'lack of project management', 'lack of protection for intellectual property rights' and 'lack of technical capability' in order to compete in the offshore outsourcing business.

A review of recent developments in carbon capture utilizing oxy‐fuel combustion in conventional and ion transport membrane systems

Abstract: Fossil fuels provide a significant fraction of the global energy resources, and this is likely to remain so for several decades. Carbon dioxide (CO2) emissions have been correlated with climate change, and carbon capture is essential to enable the continuing use of fossil fuels while reducing the emissions of CO2 into the atmosphere thereby mitigating global climate changes. Among the proposed methods of CO2 capture, oxyfuel combustion technology provides a promising option, which is applicable to power generation systems. This technology is based on combustion with pure oxygen (O2) instead of air, resulting in flue gas that consists mainly of CO2 and water (H2O), that latter can be separated easily via condensation, while removing other contaminants leaving pure CO2 for storage. However, fuel combustion in pure O2 results in intolerably high combustion temperatures. In order to provide the dilution effect of the absent nitrogen (N2) and to moderate the furnace/combustor temperatures, part of the flue gas is recycled back into the combustion chamber. An efficient source of O2 is required to make oxy-combustion a competitive CO2 capture technology. Conventional O2 production utilizing the cryogenic distillation process is energetically expensive. Ceramic membranes made from mixed ion-electronic conducting oxides have received increasing attention because of their potential to mitigate the cost of O2 production, thus helping to promote these clean energy technologies. Some effort has also been expended in using these membranes to improve the performance of the O2 separation processes by combining air separation and high-temperature oxidation into a single chamber. This paper provides a review of the performance of combustors utilizing oxy-fuel combustion process, materials utilized in ion-transport membranes and the integration of such reactors in power cycles. The review is focused on carbon capture potential, developments of oxyfuel applications and O2 separation and combustion in membrane reactors. The recent developments in oxyfuel power cycles are discussed focusing on the main concepts of manipulating exergy flows within each cycle and the reported thermal efficiencies. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of nanocomposites and amorphous alloys by mechanical alloying

Abstract: Mechanical alloying (MA) is a powder metallurgy processing technique that involves repeated cold welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Due to the specific advantages offered by this technique, MA was used to synthesize a variety of advanced materials. This article presents two specific examples of synthesis of nanocomposites containing a high volume fraction of the reinforcement phase in Al and TiAl matrices. It was possible to uniformly disperse 50 vol% of nanometric (50 nm) Al2O3 in Al and achieve high strength and modulus of elasticity. Similarly, it was possible to disperse 60 vol% of Ti5Si3 phase in the γ-TiAl intermetallic. Fully consolidated material showed superplastic behavior at 950 °C and a strain rate of 4 × 10−5 s−1. Amorphous phases were produced by MA of blended elemental powder mixtures in several Fe-based compositions. From the systematic investigations carried out, it was possible to deduce the criteria for glass formation and understand the interesting phenomenon of mechanical crystallization. By conducting some controlled experiments, it was also possible to explain the mechanism of amorphization in these mechanically alloyed powder blends. Other examples of synthesis of advanced materials, e.g., photovoltaic materials and energetic materials, have also been briefly referred to. This article concludes with an indication of the topics that need special attention for further exploitation of these materials.

A Dual-Input Digitally Driven Doherty Amplifier Architecture for Performance Enhancement of Doherty Transmitters

Abstract: In this paper, the novel architecture of a dual-input and digitally driven Doherty amplifier is proposed with the aim of improving the performance of gallium-nitride (GaN) Doherty transmitters. In this work, the power efficiency is enhanced by using digital adaptive phase alignment to compensate for performance degradation due to bias and power-dependant phase misalignment between the carrier and peaking branches. For experimental validation, the proposed dual-input digital Doherty power amplifier (PA) was implemented using a 10-W GaN transistor. Measurement results demonstrate that the dual-input Doherty prototype exhibited a power-added efficiency (PAE) higher than 50% over an 8-dB output power back-off (OPBO) range. In comparison with the conventional fully analog Doherty PA, this represents a 10% improvement in PAE over the same OPBO range. Using a one-carrier Worldwide Interoperability for Microwave Access signal with a 7-dB peak-to-average power ratio, the dual-input Doherty PA, with digital adaptive phase alignment applied at the input of its peaking path, achieved a PAE of 57% at an average output power of 37.8 dBm, along with a - 22-dBc adjacent channel power ratio (ACPR). This corresponds to an improvement of 7% in PAE and 1 dB in average output power for the same ACPR level in comparison with a conventional fully analog Doherty PA.