Analytical solution to continuous contact problem for a functionally graded layer loaded through two dissimilar rigid punches

A continuous contact problem of functionally graded layer resting on an elastic semi-infinite plane, which is loaded with through two different blocks is addressed in this study. The elasticity theory and integral transformation techniques are used in solution of the problem. The problem is reduced to a system of singular integral equations, and solved numerically by the aid of appropriate Gauss–Chebyshev integration formula. It is assumed that the elastic semi-infinite homogeneous plane is isotropic and all surfaces are frictionless and continuous. The shear modulus and the mass density of the FG layer vary exponentially along the thickness direction.     

Fast removal of methylene blue (MB) with functionalized resin

Herein, a new adsorbent was developed in order to fast and effective removal of MB from aqueous solution. For this, crosslinked maleic anhydride polymer was synthesized by copolymerization of maleic anydride (MA) with divinyl benzene (DVB) in DMF at 75?°C using a radical initiator AIBN. A new functionalized resin containing carboxylic acid groups was prepared with modification of crosslinked maleic anydride resin with 5-aminoisophthalic acid. Prepared resin was characterized with FTIR, TGA/DTA and SEM. Parameters affecting adsorption such as pH, initial dye concentration and adsorption time, and also, different isotherm and kinetic models were studied. It was observed that synthesized resin could be used to MB fast removal wide pH and concentration range very high efficiency. It was also found to be that Freundlich isotherm model (R² = 0.9993) and second order kinetic models are much more suitable for adsorption of MB. Moreover, it was also observed that synthesized resin could be used at least five times without losing its original activity.     

MIL‐53(Al) as a Versatile Platform for Ionic‐Liquid/MOF Composites to Enhance CO2 Selectivity over CH4 and N2

Five different imidazolium‐based ionic liquids (ILs) were incorporated into a metal–organic framework (MOF), MIL‐53(Al), to investigate the effect of IL incorporation on the CO₂ separation performance of MIL‐53(Al). CO₂, CH₄, and N₂ adsorption isotherms of the IL/MIL‐53(Al) composites and pristine MIL‐53(Al) were measured to evaluate the effect of the ILs on the CO₂/CH₄ and CO₂/N₂ selectivities of the MOF. Of the composite materials that were tested, [BMIM][PF₆]/MIL‐53(Al) exhibited the largest increase in CO₂/CH₄ selectivity, 2.8‐times higher than that of pristine MIL‐53(Al), whilst [BMIM][MeSO₄]/MIL‐53(Al) exhibited the largest increase in CO₂/N₂ selectivity, 3.3‐times higher than that of pristine MIL‐53(Al). A comparison of the CO₂ separation potentials of the IL/MOF composites showed that the [BMIM][BF₄]‐ and [BMIM][PF₆]‐incorporated MIL‐53(Al) composites both showed enhanced CO₂/N₂ and CO₂/CH₄ selectivities at pressures of 1–5 bar compared to composites of CuBTC and ZIF‐8 with the same ILs. These results demonstrate that MIL‐53(Al) is a versatile platform for IL/MOF composites and could help to guide the rational design of new composites for target gas‐separation applications.     

Thermal and electrical behaviors of acid functionalized MWCNT/ABC-type triblock copolymer grafted-MWCNT nanocomposites

In this work, ABC-type triblock copolymer grafted onto the surface of the MWCNT/acid functionalized MWCNT (MWCNT-COOH) composites were prepared and the properties of nanocomposites were characterized extensively using differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), ac electrical conductivity and dielectrical measurements.

DSC study showed that the glass transition temperatures of the nanocomposites are a some higher than that of the matrix polymer. The increase in oxidized MWCNT in the nanocomposite improved the thermal stability of the composite, according to initial decomposition temperatures. The ac electrical conductivity has increased moderately with increasing frequency, but has increased slowly with increase in the oxidized MWCNT content in the nanocomposites. The electrical conductivity increases slowly with increasing temperature to about the glass transition temperature, then it increases faster. The dielectric constants for the matrix polymer and all the composites decreases slightly with increasing frequency from 0.1 kHz to 2.0 kHz. The dielectric constant increases slightly with increasing temperature up to about the glass transition temperature region and then the increase in temperature is accelerated the increase in the dielectric constant.     

Determination of Melatonin Hormone and Neurotransmitters in Cerebrospinal Fluid: Method Validation and Uncertainty Calculations

The uncertainty of measurement for well-known neurotransmitters like serotonin, noradrenalin and gamma-aminobutyric acid (GABA), glutamate and melatonin hormone with high performance liquid chromatography?fluorescence detection was calculated after the method validation. Two methods were developed for the determination of the neurotransmitters. A derivatization step was performed for the determination of GABA and glutamate. Sensitivity, method detection limit, limit of quantification, linearity, recovery, interday and intraday precision values were calculated. Low detection limit values were obtained especially for the determination of GABA and glutamate. Then, bottom-up approach was used to calculate measurement uncertainty. The critical stages of the method were evaluated. The major sources of the uncertainty budget were calibration curves, stock solution and recovery. The calculated percentage relative uncertainty values for the compounds changed between 10.1 and 16.7.     

CO-releasing properties and anticancer activities of manganese complexes with imidazole/benzimidazole ligands

Carbon monoxide (CO) is an important signaling molecule which plays significant roles in the pathogenesis of cancer. CO is produced by enzymatic degradation of heme in mammals. Heme oxygenase 1 (HO-1) catalyzes the breakdown of heme into CO, ferrous iron, and biliverdin. CO induces HO-1 and inhibits cell proliferation. Cancer cells exposed to several stress factors (hypoxia, reactive oxygen species, cis-platin, and oxidative stress), and HO-1 displays cytoprotective role against oxidative stress and inhibits apoptosis, metastases, angiogenesis, and cell proliferation processes. Therefore, metal containing CO-releasing molecules (CORMs) have been designed as an effective cancer treatment strategy. CORMs are responsible for releasing controlled amounts of CO to cells and tissues. Thus, we synthesized [Mn(CO)₃(bpy)L]X manganese containing CORMs [bpy = 2,2′-bipyridine, X = hexafluorophosphate (PF₆), trifluoromethanesulfonate (OTf), L = imidazole, methylimidazole, benzimidazole, N-benzylbenzimidazole, N-(4-chlorobenzyl)benzimidazole] to release CO in human invasive ductal breast (MCF-7) cell line. In vitro experiments indicated that the compounds inhibited cell proliferation and exhibited cytotoxic effect on breast cancer cells. Moreover, side groups of the compounds enhanced the anticancer effects in MCF-7 cell line. These manganese containing CORMs gave promising results and may be used as a drug template for effective treatment of invasive ductal breast carcinoma.     

Colorings of infinite graphs without one-colored rays

The R-chromatic number of a graph G is the least number of subsets of vertices forming a partition of V(G), and which induce subgraphs of G without infinite paths. For any integer n ≥ 2, we give sufficient conditions for a graph containing no subdivision of an infinite complete graph to have a R-chromatic number ≤ n. © 1996 John Wiley & Sons, Inc.     

Graphs without isometric rays and invariant subgraph properties,I

A ray of a graph G is isometric if every path in R is a shortest path in G. A vertex x of G geodesically dominates a subset A of V(G) if, for every finite S ⊆ V(G − x), there exists an element a of A − {x} such that the interval (set of vertices of all shortest paths) between x and a is disjoint from S. A set A ⊆ V(G) is geodesically closed if it contains all vertices which geodesically dominate A. These geodesically closed sets define a topology, called the geodesic topology, on V(G). We prove that a connected graph G has no isometric rays if and only if the set V(G) endowed with the geodesic topology is compact, or equivalently if and only if the vertex set of every ray in G is geodesically dominated. We prove different invariant subgraph properties for graphs containing no isometric rays. In particular we show that every self-contraction (map which preserves or contracts the edges) of a chordal graph G stabilizes a non-empty finite simplex (complete graph) if and only if G is connected and contains no isometric rays and no infinite simplices. © 1998 John Wiley & Sons, Inc. J Graph Theory 27: 99–109, 1998     

Monte Carlo simulations and forecasting of Radium-226, Thorium-232, and Potassium-40 radioactivity concentrations

Journal of Radioanalytical and Nuclear Chemistry - This study depicts the radioactivity time series levels of 226Ra, 232Th, and 40K prospectively by Monte Carlo simulations (MCSs). Three ARIMA...     

The effect of metal work function on the barrier height of metal/CdS/SnO2/In–Ga structures

In order to interpret the effect of metal work function on the formation of the barrier height at metal/semiconductor (M/S) interface, the CdS/SnO₂/In–Ga structures with several metals (Ag, Au, Al, Te) have been investigated by using I–V characteristics at room temperature. The main electrical parameters such as ideality factor (n), zero-bias barrier height (Φ_Bo), series resistance (R_s) have been determined and compared with each other. The values of n were found to be 3.00, 2.56, 3.83, and 3.31 for Al, Ag, Te, and Au/CdS/SnO₂/In–Ga structures, respectively. The values of Φ_Bo were also found to be 0.489 eV, 0.490 eV, 0.583 eV, 0.591 eV for Al, Ag, Te, and Au/CdS/SnO₂/In–Ga structures, respectively. The Φ_Bo dependence on the metal work function (Φ_m) was found to vary almost linearly as Φ_Bo = 0.106Φ_m + 0.028. The low value of the slope S (dΦ_B/dΦ_M ? 0.106) shows a weak relationship between Φ_Bo and Φ_m due to serious Fermi-level pinning in the conduction band. In addition, the I–V plots have a rectifying behavior. The rectification ratio, defined by the ratio of forward to reverse current (RR = I_F/I_R) measured at the same absolute bias, was found as 11.96, 20.88, 35.82, and 75.61 for Al, Ag, Te, Au/CdS/SnO₂/In–Ga diodes, respectively. In addition, the values of R_s were determined from Ohm's Law and Norde's method. Analysis of I–V characteristics confirm that using of different metal (Al, Ag, Te, Au) has significant effect on electrical parameters of such devices.