Comparison of the anti-bacterial activity on the nanosilver shapes: Nanoparticles,nanorods and nanoplates

In this study, we comparison of the antimicrobial activity on the nanosilver shapes; Ag-nanoplates (Ag-NPls), Ag-nanorods (Ag-NRds) and Ag-nanoparticles (Ag-NPs). Nanosilver shapes were prepared with a stabilizer, such as poly (N-vinyl-2-pyrrolidone) (PVP). Antimicrobial effect of nanosilver shapes for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was investigated using disc diffusion and minimum inhibitory concentration (MIC) methods. The growth of Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria were inhibited by nanosilver shapes. With BET technique, it was found that surface area of nanosilver shapes are key factor for controlling antimicrobial activity inside of the S. aureus and E. coli bacteria. Anti-bacterial activity of nanosilver shapes was found to be dependent on the shape and size of silver particles. Also, the Ag-NPls did show the best surface area and antimicrobial activity for the test organisms. The scanning electron microscopy (SEM), indicated that, the most strains of S. aureus and E. coli were damaged and extensively disappeared by addition of Ag-NPls.     

Geotechnical properties of steel slag aggregates: Shear strength and stiffness

Steel slag is an industrial by-product formed in the furnace during the steelmaking process. Electric arc furnace slag (EAFS) and ladle furnace slag (LFS) are the primary by-products of steelmaking from steel scraps. This research evaluates the physical, geotechnical and engineering properties of LFS, EAFS and a blend comprising 50% LFS and 50% EAFS (LFS50 + EAFS50) through laboratory testing. The specialized laboratory tests undertaken in this study include California bearing ratio (CBR) and unconfined compressive strength (UCS) tests, direct shear tests (DSTs), consolidated drained (CD) triaxial tests and repeated load triaxial (RLT) tests. The shear strength responses of the steel slag were found to vary with the dilatancy-induced peak strength of the LFS and the LFS50 + EAFS50 mixture and the dilatancy-associated strain-hardening behavior of the EAFS. Based on the high shear strength parameters and the adequate stiffness that were attained, the steel slag was found to have the potential for usage as a geo-material. LFS and LFS50 + EAFS50 were well-graded and had high CBR values, which would deem them suitable for roadwork applications. EAFS, however, was found to be poorly graded and to have relatively lower CBR values, which would deem it suitable for less stringent applications such as engineering fill and pipe bedding. The viability of using these by-products as geo-materials in civil infrastructures can transform these current waste by-products, particularly LFS, from being stockpiled at steel company plants to being used as alternative green material.     

CO2 biofixation by Synechococcus elongatus from the power plant flue gas under various light–dark cycles

Clean Technologies and Environmental Policy - Carbon dioxide emission, which acts as one of the major agents of greenhouse gases (GHG), has significant effects on global warming. Nowadays, there is...     

Radius of Curvature and Entraining Velocity of Cam Follower Mechanisms

A general procedure for determining the equivalent radius of curvature and entraining velocity of various oscillating and reciprocating cam and follower mechanisms has been developed. This procedure requires as input the motion of the follower, i.e., the lift curve, the angular velocity of the cam and the basic geometry of the cam and follower mechanism. The radius of curvature of the cam at the point of contact was determined using the method of kinematic coefficients. A vector loop superimposed on the cam and follower was used to determine the entraining velocity of the mechanism at the point of contact.     

Improving surface integrity in finish machining of Inconel 718 alloy using intelligent systems

In machining of hard materials, surface integrity is one of the major customer requirements which comprise the study of the changes induced to the workpiece. Surface roughness and residual stress are often considered as the most significant indications of surface integrity. Inducing tensile residual stress during the machining processes is a critical problem which should be avoided or minimized to obtain better service quality and component life. This problem becomes more evident in the presence of rough machined surface because fatigue life of manufactured components might be decreased significantly. Inconel 718 superalloy is one of the hard materials used extensively in the aerospace industries. It is prone to tensile residual stress in machined surface. Thus, controlling and optimizing residual stress and surface roughness in machining of Inconel 718 are so needed. Intelligent techniques based on the predictive and optimization models can be used efficiently for this purpose. In this study, the optimal machining parameters including cutting speed, depth of cut, and feed rate were accessed by intelligent systems to evaluate the state of residual stress and surface roughness in finish turning of Inconel 718. The results of experiments and analyses indicated that implemented techniques in this work provided a robust framework for improving surface integrity in machining of Inconel 718 alloy. It was shown that cutting speed has more effect on surface integrity than other investigated parameters. Also, depth of cut and feed rate were found in the moderate range to obtain satisfactory state of tensile residual stress and surface roughness.     

Aqueous free-radical polymerization of PEGMEMA macromer: kinetic studies via an on-line 1H NMR technique

Free-radical polymerization of polyethylene glycol methyl ether methacrylate macromer (PEGMEMA) was studied in aqueous media and in the presence of potassium persulfate (KPS) as water soluble initiator. An on-line nuclear magnetic resonance (NMR) method was applied to record the reaction data and determine the monomer conversion at various times during the polymerization reaction progress. ¹H NMR spectrum of reaction mixture containing monomer, initiator and resultant polymer was continuously recorded in NMR instrument with the increase of reaction time. By processing the obtained data from NMR spectrum, the rate equation can be derived and reaction order can be determined with regard to monomer and initiator concentration. In other words, to determine the order of polymerization with regard to the concentration of reactants in free-radical polymerization of PEGMEMA, macromer samples with different amounts of monomer and KPS were prepared and polymerized at 50?°C. Orders of reaction with respect to monomer and initiator molar concentrations were equal to 1.025 and 0.480, respectively. The obtained values for reaction orders in this study were consistent with the classical kinetic rate equation in which the dependency of polymerization rate (R _p) on monomer and initiator concentrations was equal to 1 and 0.5, respectively. To measure polymerization activation energy (E _a), the effect of reaction temperature on the polymerization rate was investigated and E _a?=?37.08?kJ/mol was obtained at the temperature range of 40?C50?°C.     

Membrane bioreactor for treatment of pharmaceutical wastewater containing acetaminophen

Treatment of pharmaceutical wastewater is a real challenge for wastewater engineers. In this study, a pilot-scale system including an external loop airlift membrane bioreactor (ELAMBR) was applied for treatment of a synthetic pharmaceutical wastewater. The performance of this system was evaluated in removal of acetaminophen as the main pollutant of a pharmaceutical wastewater. A conventional activated sludge (CAS process) laboratory system was used in parallel with this system to compare both systems in regard to their ability for acetaminophen removal. The performance of the ELAMBR system was monitored for approximately one month to investigate the long-term operational stability of the system and possible effects of solids retention time on the efficiency of removal of acetaminophen. The removal efficiency was significantly higher in the ELAMBR system than the CAS process. 100% of the acetaminophen was removed after 2 days in this system. The results also showed that initial concentration of acetaminophen, chemical oxygen demand (COD) and mixed liquid suspended solids (MLSS) are the most effective parameters in removal of a pollutant such as acetaminophen. This study demonstrates the usefulness of ELAMBR system for pharmaceutical wastewater treatment with the advantages such as: (i) simple operation and maintenance, (ii) efficient removal of pharmaceutical pollutant and COD and (iii) low-energy consumption.     

Analytical Models for Single-Hop and Multi-Hop Ad Hoc Networks

There is considerable interest in modeling the performance of ad hoc networks analytically. This paper presents approximate analytical models for the throughput performance of single-hop and multi-hop ad hoc networks. The inherent complexity of analysis of a multi-hop ad hoc network together with the fact that the behavior of a node is dependent not only on its neighbors' behavior, but also on the behavior of other unseen nodes makes multi-hop network analysis extremely difficult. However, our approach in this paper to analyze multi-hop networks offers an accurate approximation with moderate complexity. Our approach is based on characterizing the behavior of a node by its state and the state of the channel it sees. This approach is used to carry out an analysis of single-hop and multi-hop ad hoc networks in which different nodes may have different traffic loads. In order to validate the model, it is applied to IEEE 802.11-based networks, and it is shown through extensive simulations that the model is very accurate. Farshid Alizadeh-Shabdiz received his B.Sc. in 1989 at University of Science and Technology, M.Sc. in 1991 at Tehran University, Iran, and D.Sc. in 2004 at the George Washington University. He is a senior research engineer in Advanced Solution Group, part of Cross Country Automotive Services, and he is also a part time faculty member at Boston University. Dr. Alizadeh-Shabdiz was part of the design and implementation team of the three first satellite-based mobile networks: ICO global medium orbit satellite network voice and data services, Thuraya GEO satellite network, and the first phase of Inmarsat high speed data network. His research interests include MAC layer, physical layer and network layer of wireless and satellite networks. Suresh Subramaniam received the Ph.D. degree in electrical engineering from the University of Washington, Seattle, in 1997. He is an Associate Professor in the Department of Electrical and Computer Engineering at the George Washington University, Washington, DC. His research interests are in the architectural, algorithmic, and performance aspects of communication networks, with particular emphasis on optical and wireless ad hoc networks. Dr. Subramaniam is a co-editor of the books “Optical WDM Networks – Principles and Practice” and “Emerging Optical Network Technologies: Architectures, Protocols, and Performance”. He has been on the program committees of several conferences including Infocom, ICC, Globecom, and Broadnets, and served as TPC Co-Chair for the 2004 Broadband Optical Networking Symposium. He currently serves on the editorial boards of Journal of Communications and Networks and IEEE Communications Surveys and Tutorials. He is a co-recipient of the Best Paper Award at the 1997 SPIE Conference on All-Optical Communication Systems.     

Fracture Model for Flexural Failure of Beams Retrofitted with CARDIFRC

A new retrofitting technique based on a material [Cardiff Fiber Reinforced Concrete (CARDIFRC)] compatible with concrete has been developed at Cardiff University. It overcomes some of the problems associated with the current techniques based on externally bonded steel plates and fiber-reinforced plastic laminates which are due to the mismatch of their tensile strength and stiffness with that of the concrete structure being retrofitted. CARDIFRC is characterized by high tensile/flexural strength and high energy-absorption capacity (i.e., ductility). The special characteristics of CARDIFRC make it particularly suitable for repair, remedial and upgrading activities (i.e., retrofitting) of existing concrete structures. It has been shown that damaged reinforced concrete beams can be successfully strengthened and rehabilitated in a variety of different retrofit configurations using precast CARDIFRC strips adhesively bonded to the prepared surfaces of the damaged beams. To predict the moment resistance of the beams retrofitted in this manner an analytical model is introduced in the present paper. This model takes a fracture mechanics approach and follows the initiation and growth of the flexural crack that eventually leads to the failure of the retrofitted beams. The results of this analytical model are found to be in very good agreement with the test results.     

Friction Force Microscopy of Lubricin and Hyaluronic Acid between Hydrophobic and Hydrophilic Surfaces

Lubricin and hyaluronic acid (HA), molecular constituents of synovial fluid, have long been theorized to play a role in joint lubrication and wear protection. While lubricin has been shown to function as a boundary lubricant, conflicting evidence exists as to the boundary lubricating ability of hyaluronic acid. Here, we use colloidal force microscopy to explore the friction behavior of these two molecules on the microscale between chemically uniform hydrophilic (hydroxyl-terminated) and hydrophobic (methyl-terminated) surfaces in physiological buffer solution. Behaviors on both surfaces are physiologically relevant since the heterogeneous articular cartilage surface contains both hydrophilic and hydrophobic elements. Friction between hydrophobic surfaces was initially high (μ=1.1, at 100nN of applied normal load) and was significantly reduced by lubricin addition while friction between hydrophilic surfaces was initially low (μ=0.1) and was slightly increased by lubricin addition. At lubricin concentrations above 200 μg/ml, friction behavior on the two surfaces was similar (μ=0.2) indicating that nearly all interaction between the two surfaces was between adsorbed lubricin molecules rather than between the surfaces themselves. In contrast, addition of HA did not appreciably alter the frictional behavior between the model surfaces. No synergistic effect on friction behavior was seen in a physiological mixture of lubricin and HA. Lubricin can equally mediate the frictional response between both hydrophilic and hydrophobic surfaces, likely fully preventing direct surface-to-surface contact at sufficient concentrations, whereas HA provides considerably less boundary lubrication.