Separation of CO2 from CH4 using a synthesized Pebax-1657/ZIF-7 mixed matrix membrane

In this study, ZIF-7 nanoparticles were first synthesized and then incorporated into polyether-block-amide (Pebax-1657) matrix with different loadings to prepare mixed matrix membranes. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses were employed to recognize crystalline structure and chemical bonds variations of the ZIF-7 nanoparticles, respectively. Morphology of the membrane exhibited that the best performance was observed using FESEM analysis. The CO₂ and CH₄ permeation experiments were carried out at temperature and pressure of 30°C and 2.5 bar, respectively. The gas permeation results indicated that the mixed matrix membranes have higher efficiencies for CO₂/CH₄ separation compared with the neat membranes.     

Enhanced performance through a dual isolation seismic protection system

While base isolation successfully decreases the accelerations transmitted to a structure, a tradeoff is large unfavorable displacements in the isolation layer. This study investigates an innovative system, termed ‘dual isolation’, which applies two layers of isolation at the base and at mid‐story to resolve this issue. A linear analytical solution for the equation of motion of the proposed system is developed on the basis of linear isolation theory. This creates a foundation to assess the behavior of various types of seismic protection systems and to select the damping and mass ratio that optimizes the performance of the proposed method. Dynamic response of an example dual isolated system to selected suites of ground motions is then examined. In addition to decreasing the displacement of the first isolation layer, the dual isolation system can greatly decrease floor accelerations of the upper portion of the building, further protecting building components and enhancing the comfort and safety of residents. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Pulsed Current Frequency on Morphology and Corrosion Behavior of Plasma Electrolytic Oxidation on Aluminum

Protection of Metals and Physical Chemistry of Surfaces - Protective oxide coatings are developed on aluminum substrate through plasma electrolytic oxidation using a pulsed current and within the...     

Correlation of source rocks and crude oils in Kupal and its near oil fields,SW of Iran

The Kupal oil field is located in the north of Dezful Embayment in southwest of Iran. The purposes of this study were correlations between the Sarvak and Asmari reservoirs oils in the Kupal oil field and determining the source of oil in this field. In order to achieve these objectives, different geochemical methods, including Rock Eval, gas chromatography, gas chromatography-mass spectrometry, and carbon isotope analyses of asphalthene in oils and source rocks, were used. The results of pyrolyzed possible source rocks of the Kupal and its near fields by the Rock Eval apparatus indicated good source rock potential for the Kazhdumi and Pabdeh formations. In addition, Kazhdumi formation in the Haft-Kel oil field indicated gas production potential while the samples of the Gurpi formation were in a non-source rock zone. The Asmari and Bangestan reservoir oils had the same components and geochemical characteristics, except the Sarvak (Bangestan) reservoir oil in the Kupal field contained Oleanane biomarkers, whereas Asmari reservoir oil had no Oleanane biomarker. This fact was attributed to the fault in the southwestern part of the Kupal oil field, which moved the Pabdeh formation (in which its oil contains Oleanane biomarkers) to more depths and near the Sarvak formation. This movement caused the maturation of Pabdeh formation and migration of the produced oil to the Sarvak reservoir.     

Deriving and Evaluating Bathymetry Maps and Stage Curves for Shallow Lakes Using Remote Sensing Data

Urmia Lake as a most vital water bodies in Iran, has been shrinking since the late twentieth century and its area has dramatically decreased. To develop and apply any plans to survive the lake, qualitative and quantitative analysis and any modeling, deriving physical information such as volume, area and their changes are very crucial. The objectives of this study were therefore, intended firstly, to study the bathymetry of Urmia Lake with a more satisfactory approach using Landsat- LDCM satellite image and in situ measurement data. The polynomial model was developed to predict the water depth in Urmia Lake area. This model was developed with the input series of reflectance values from blue, green, red and NIR bands in the Landsat- LDCM satellite imagery for Urmia Lake taken on 12 April 2013 of the sampling sites from actual depth measured were taken on the same date. Also, using a large archive of Landsat imagery (TM, ETM+ and LDCM), a counter of equivalent elevation were established for deriving the bathymetry of desiccated areas by mapping the edges of the lake and finally assembled with bathymetry derived from polynomial model. In-situ depth measurements were used to evaluate resultant derived bathymetric map. This comparison shows reasonable agreement between the Landsat-derived depths and those measured in the field with RMSE of 0.27 cm and R² = 0.91. The maximum and mean depths measured were 4.9 and 11 m respectively. The maximum depth measured was located at the upper part of the lake. As well as, developed multi-regression equation used for deriving another bathymetry map using Landsat- LDCM satellite image taken on Sep. 2015 for salt deposition monitoring. Results indicates that about 64 cm salt deposition has occurred during the last two years. Secondly, to make stage curves of lake, multi-temporal changes of water body have been derived from Landsat, MODIS and AVHRR satellite images sets since 1972. In this regard, the area of Urmia Lake at different level was estimated base on object oriented and pixel base classification using 78 satellite images. Finally, stage curve (volume- area- level relations) was derived from bathymetry map.     

Alkaline pH does not disrupt re-assembled casein micelles

Characteristics of re-assembled casein micelles were investigated over a broad pH range from 6.35 to 11.4. Turbidity of casein solution decreased as pH increased. The higher the pH, the lower was the turbidity value. This decrease in turbidity was concomitant with the increased diameter of micelles which is attributed to the increased electrostatic repulsion amongst casein molecules and the solvent quality of serum phase. It is hypothesised that looser expanded structure of casein micelles with smaller specific surface area available for light scattering led to a decrease in the observed turbidity of casein solutions with increasing pH. Swelling of re-assembled casein micelles at higher pH values increased the consistency coefficient of casein solutions, indicating an increase in their apparent viscosity.     

The Minimum Vulnerability Problem

We revisit the problem of finding \(k\) paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the \(k\) paths. We provide a \({\lfloor {k/2}\rfloor }\) -approximation algorithm for this problem, improving the best previous approximation factor of \(k-1\) . We also provide the first approximation algorithm for the problem with a sublinear approximation factor of \(O(n^{3/4})\) , where \(n\) is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be improved to \(O(\sqrt{n})\) . While the problem is NP-hard, and even hard to approximate to within an \(O(\log n)\) factor, we show that the problem is polynomially solvable when \(k\) is a constant. This settles an open problem posed by Omran et al. regarding the complexity of the problem for small values of \(k\) . We present most of our results in a more general form where each edge of the graph has a sharing cost and a sharing capacity, and there is a vulnerability parameter \(r\) that determines the number of times an edge can be used among different paths before it is counted as a shared/vulnerable edge.     

Exact reliability evaluation of infrastructure networks using graph theory

Reliability analysis of Infrastructure Networks (INs) is gaining recognition in the research literature. However, most of the work on reliability evaluation of INs have focused on simulation analysis and, therefore, unable to calculate the exact reliability. Additionally, these methods lack the capability of achieving a closer adherence to INs. The presented paper aims at filling these gaps by simplifying the process of computing the exact reliability of an IN through the decomposition of the network into a set of series and parallel configuration of its elements. In exemplifying the method, an illustrative example is presented and a brief discussion on the usefulness and limitation of the method is described.     

The indentation of pressurized elastic shells: from polymeric capsules to yeast cells

Pressurized elastic capsules arise at scales ranging from the 10 m diameter pressure vessels used to store propane at oil refineries to the microscopic polymeric capsules that may be used in drug delivery. Nature also makes extensive use of pressurized elastic capsules: plant cells, bacteria and fungi have stiff walls, which are subject to an internal turgor pressure. Here, we present theoretical, numerical and experimental investigations of the indentation of a linearly elastic shell subject to a constant internal pressure. We show that, unlike unpressurized shells, the relationship between force and displacement demonstrates two linear regimes. We determine analytical expressions for the effective stiffness in each of these regimes in terms of the material properties of the shell and the pressure difference. As a consequence, a single indentation experiment over a range of displacements may be used as a simple assay to determine both the internal pressure and elastic properties of capsules. Our results are relevant for determining the internal pressure in bacterial, fungal or plant cells. As an illustration of this, we apply our results to recent measurements of the stiffness of baker''s yeast and infer from these experiments that the internal osmotic pressure of yeast cells may be regulated in response to changes in the osmotic pressure of the external medium.     

Multifunctional nanoporous magnetic zinc silicate-ZnFe2O4 core-shell composite for bone tissue engineering applications

Multifunctional materials have recently gained substantial attraction in bone tissue engineering because of their capabilities to solve essential problems after implantation including inflammation and osteomyelitis and also bone cancerous tissues through hyperthermia treatment. The aim of this study was to design and develop a new multifunctional composite containing a magnetic zinc ferrite as a core, and nanoporous zinc silicate as a shell via a two-step synthesis strategy to meet all above targets simultaneously. ZnFe₂O₄ particles are synthesized via solvothermal method and then coated through surfactant-assisted sol-gel method to obtain zinc silicate-ZnFe₂O₄ composite using cetyltrimethylammoniumbromide (CTAB) as a surfactant. The XRD results show that the composite has a glass-ceramic structure. The FESEM micrographs indicate the increase in the size of ZnFe₂O₄ particles because of zinc silicate formation around them. The vibrating sample magnetometer (VSM) results reveal that the formation of zinc silicate over ZnFe₂O₄ particles caused the magnetization saturation (Ms) to be reduced from 43 to 30?emu?g^?1. The antibacterial activity of the composite is evaluated against S. aureus and E. coli bacteria. Heat generation capability of the composite is assessed in vitro and results show that the composite reached the saturation temperature of 45?°C up to 510?s with 200?Oe magnetic field and constant 200?kHz frequency. Potential application of the composite as a controlled release system is assessed in vitro up to 240?h. The cell compatibility of the composite with different concentrations is assessed using osteoblast-like cells (MG63) up to 48?h.