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Polyacrylic acid is a biocompatible and biodegradable polymer that has been widely investigated for use in drug delivery. It has a number of properties that make polyacrylic acid a promising material for various applications, including ability to form hydrogels, mucoadhesive properties, and stimuli-responsive behavior. Polyacrylic acid hydrogels can be used to deliver drugs to a variety of tissues and organs. They can be prepared in a variety of forms, including injectable gels, films, and tablets. These hydrogels can be loaded with a variety of drugs, including proteins, peptides, and small molecules. The mucoadhesive properties of polyacrylic acid make it a good choice for delivering drugs to the eye, nose, and skin. Polyacrylic acid can adhere to these mucosal surfaces, which can help to prolong the drug's release and improve its bioavailability. The stimuli-responsive behavior of polyacrylic acid can be used to develop drug delivery systems that release drugs in response to specific stimuli, such as changes in pH, temperature, or ionic strength. This can be used to control the release of drugs in a way that is tailored to the specific needs of the patient. The research on the use of polyacrylic acid in drug delivery is ongoing. As our understanding of its properties and behavior improves, we can expect to see even more innovative and effective drug delivery systems developed in the future. [ABSTRACT FROM AUTHOR]

Biodistribution and tumour agglomeration of chemotherapeutic drugs are improved by nanoparticles augmenting the ratio of efficacy and toxicity. Iron oxide nanoparticles have attracted growing attention in diagnosis, cancer therapy, and smart drug delivery. To simplify the combined therapy and targeting drug delivery such as using ultrasound, we developed magnetoliposome-encapsulated doxorubicin. Superparamagnetic iron oxide nanoparticles and magnetoliposome-encapsulated doxorubicin were well synthesised without any remarkable mitigation of the saturation magnetisation. Doxorubicin and the synthesised iron oxide nanoparticles were passively encapsulated into PEGylated liposomes leading to stable soluble magnetoliposomes with a size of about 485 nm. The cytotoxicity of doxorubicin-loaded magnetoliposomes was examined on MCF-7 cells. Compared with chemotherapy alone, the combined therapy employing ultrasound showed a synergistic effect, giving rise to more robust cytotoxicity and higher therapeutic efficacy. Hence, the multifunctional doxorubicin-loaded magnetoliposomes permit them to selectively deliver a combinatorial therapeutic load with increased therapeutic effectiveness. [ABSTRACT FROM AUTHOR]

The objective of this research was to synthesize and evaluate novel three dimensional scaffolds composed of poly (lactic-co-glycolic acid) (PLGA)/layered double hydroxide (LDH) composite microspheres for potential bone substitute applications. The mechanical properties of the scaffolds were found to be modulated by the sintering conditions, such as sintering temperature and sintering time, and by the PLGA/LDH ratio. After optimization, the newly developed PLGA/LDH (4:1) scaffold sintered at 90 °C for 2 h exhibited the highest mechanical properties; they were higher than those of the pure polymeric scaffold and also had a desirable pore structure for bone tissue engineering applications. The preliminary examination using L929 cells carried out and no signs of cytotoxicity were observed. The culture of G-292 cells on the optimized samples via the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction assay method demonstrated increased cell proliferation compared with the pure PLGA scaffolds and the control group (a cell culture plate). Additionally, when the cells were cultured on the composite scaffolds, the osteoblasts had significantly increased alkaline phosphatase (ALP) activity relative to those on the pure PLGA scaffolds and the control group. Thus, the obtained results indicated that the PLGA/LDH microsphere-sintered scaffolds deserve attention for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

Dissipative particle dynamics simulations are performed on wet polymer nanocomposite blends under the discrete imposed velocity profile and no-slip boundary conditions. To be able to study the chain length dependency of the rheological properties, a number of blends of mono-disperse polymer chains of lengths varying from 10 to 100 repeat units and nanoparticles of diameters 2.5 and 5 have been simulated. The wall velocity was imposed on a thin polymer layer (the no-slip layer). Linear velocity profiles for polymer confined in the pore were observed at the steady state. We found that the flow has a shear thinning effect on the chains with a radius of gyration less than the filler radius. Long chains (with a radius of gyration longer than the filler's radius), however, obey the Newtonian behavior over a much wider shear rate than that which causes shear thinning in short chains. The effect of particle-monomer interactions, polymer entanglements, chain morphology, and link formation on the shear rate dependency of the viscosity coefficient has been studied. Our results show that the particle-polymer interactions have no effect on shear thinning behavior of the blend. In contrast, the long range polymer-polymer interactions and the chain length have considerable effects on the rheological behavior of the blend. Finally, the phase diagram of the rheological properties of polymer nanocomposite as a function of strain rate and the chain length is extracted. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to determine the solubility and diffusion coefficient of carbon dioxide and nitrogen in poly(methyl methacrylate) (PMMA). The solubilities of CO2 in the polymer are calculated employing our grand canonical ensemble simulation method, fixing the target excess chemical potential of CO2 in the polymer and varying the number of CO2 molecules in the polymer matrix till establishing equilibrium. It is shown that the calculated sorption isotherms of CO2 in PMMA, employing this method well agrees with experiment. Our results on the diffusion coefficients of CO2 and N2 in PMMA are shown to obey a common hopping mechanism. It is shown that the higher solubility of CO2 than that of N2 is a consequence of more attractive interactions between the carbonyl group of polymer and the sorbent. While the residence time of CO2 beside the carbonyl group of polymer is about three times higher than that of N2, the diffusion coefficient of CO2 in PMMA is higher than that of N2. The higher diffusion coefficient of CO2, compared to N2, in PMMA is shown to be due to the higher (≈3 times) swelling of polymer upon CO2 uptake. [ABSTRACT FROM AUTHOR]

There are many simulations in the literature to study the behavior of nanoconfined fluids between solid surfaces. Among them, a class of methods focuses on tuning the pore width in such a way that the fluid in confinement has the same tangential component of pressure as the bulk fluid. The main idea behind these methods is based on the ansatz that in equilibrium (between the fluid in confinement and the bulk fluid) the tangential component of pressure of the confined fluid is equal to the pressure of the bulk fluid at the same temperature. As there is no evidence in the literature on the validity of this ansatz, in this work we have performed molecular dynamics simulations on a large number of nanoconfined Lennard-Jones systems to evaluate its validity. For this purpose, big simulation boxes are chosen, to enable us to directly calculate the particle-particle interactions, and hence, reduce the long-range corrections to the local pressures and local chemical potentials in the inhomogeneous fluid. Simulating the confined fluid at an average tangential component of pressure equal to the pressure of the bulk fluid at the same temperature, we have calculated the chemical potentials in the pore and compared them with the corresponding bulk value. Our calculated results indicate that the chemical potentials in the pore show oscillatory behavior with respect to the pore width. Pronounced deviations in the chemical potentials from the corresponding bulk value are observed in narrower pores, compared to wider pores. Therefore, the results of the present simulations rule out the validity of the above-mentioned ansatz. [ABSTRACT FROM AUTHOR]

Objective(s): Artemisia absinthium is an aromatic, perennial small shrub that shows multiple medical benefits, including anticancerous, neuroprotective, antifungal, hepatoprotective, antidepressant and antioxidant properties. One of the effective approaches to treat Alzheimer's disease is targeting amyloid aggregation by antiamyloid drugs. In the current research study, an excellent grouping of niosomal, lipid nano-carriers drugs containing artemisia absinthium is advanced and characterized to inhibit amyloid aggregation. Materials and Methods: Niosomal vesicles were made employing phosphatidylcholine, span 60, cholesterol and DSPE-PEG2000 by the thin-film method. Then artemisia absinthium was loaded into the niosomes. Their physico-chemical attributes were analyzed utilizing Zeta-Sizer, FTIR, and SEM, and the amount of drug release was measured at 37° C. Finally, the inhibitory effect of artemisia absinthium that loaded niosomal vesicles on the aggregation of amyloid-β peptides was investigated using Thioflavin T fluorescence measurements and atomic force microscopy. Results: Niosomes containing artemisia absinthium have a size of 174±2.56nm, the encapsulation efficiency of 66.73%, zeta potential of -26.5±1/42 mV and polydispersity index (PDI) of 0.373±0/02. The release of the drug is controlled in this nano-carrier and FTIR and SEM investigations showed that the drug and nano-carrier did not interact and their particles had a spherical structure. In the end, the inhibitory effect of artemisia absinthium that loaded niosomal vesicles on the aggregation of amyloid-β peptides was examined and confirmed through Thioflavin T fluorescence measurements and atomic force microscopy. Conclusion: Meanwhile, the findings of the current study, confirm the appropriate physicochemical features of the system, a slow-release system, show that this nano-carrier inhibits amyloid aggregation, thus, the nano-niosomes containing essential oil from artemisia absinthium has the capability to preclude amyloid development. [ABSTRACT FROM AUTHOR]

The purpose of this research is to design an educational effectiveness model for the employees of the selected organization with a system dynamics approach in Iran. In order to achieve the research goal, a sequential mixed method has been used, which includes two qualitative and quantitative parts. In the qualitative part of the research, interview has been used. Necessary information and data were collected from experts and senior managers of the selected organization and then the design of the educational effectiveness model for the employees of the selected organization with a dynamic system approach has been validated. The research results showed that the educational effectiveness model for the employees of selected organization with a system dynamics approach has two parts: the main factors and their indicators. This model has been composed of indicators that are the core and heart of this model and are the basis for evaluating the educational effectiveness, which are called effective factors. The educational effectiveness model for the employees of the selected organization with a system dynamics approach has 7 main factors: learner's readiness, training need assessment, training targeting, training program design, resources and equipment allocation, course monitoring and evaluation and training course management, which includes 56 indicators composing it. [ABSTRACT FROM AUTHOR]

While polymers are known as thermal insulators, recent studies show that stretched single chains of polymers have a very high thermal conductivity. In this work, our new simulation scheme for simulation of heat flow in nanoconfined fluids [H. Eslami, L. Mohammadzadeh, and N. Mehdipour, J. Chem. Phys. 135, 064703 (2011)] is employed to study the effect of chain ordering (stretching) on the rate of heat transfer in polyamide-6,6 nanoconfined between graphene surfaces. Our results for the heat flow in the parallel direction (the plane of surfaces) show that the coefficient of thermal conductivity depends on the intersurface distance and is much higher than that of the bulk polymer. A comparison of results in this work with our former findings on the heat flow in the perpendicular direction, with the coefficient of heat conductivity less than the bulk sample, reveal that well-organized polymer layers between the confining surfaces show an anisotropic heat conduction; the heat conduction in the direction parallel to the surfaces is much higher than that in the perpendicular direction. The origin of such anisotropy in nanometric heat flow is shown to be the dramatic anisotropy in chain conformations (chain stretching) beside the confining surfaces. The results indicate that the coefficients of heat conductivity in both directions, normal and parallel to the surfaces, depend on the degree of polymer layering between the surfaces and the pore width. [ABSTRACT FROM AUTHOR]

A new molecular dynamics simulation method, with coupling to external baths, is used to perform equilibrium simulations on polyamide-6,6 trimers nanoconfined between graphene surfaces, in equilibrium with the bulk polymer. The method is coupled with the reverse nonequilibrium molecular dynamics simulation technique to exchange heat in the direction normal to the surfaces. To be able to study the effect of confinement on the heat conductance in nanoconfined pores, in this work a number of simulations on systems with different pore sizes are done. It is concluded that the coefficient of heat conductivity depends on the degree of polymer layering between the surfaces and on the pore width. Our results further indicate a considerable temperature drop at the interface between the surfaces and polymer. The calculated Kapitza lengths depend on the intersurface distance and on the layering of the polymer nanoconfined between the surfaces. [ABSTRACT FROM AUTHOR]

A method for performing molecular dynamics simulation in the grand canonical ensemble is developed. The molecular dynamics, with coupling to an external bath, simulation method of [Berendsen et al., J. Chem. Phys. 81, 3684 (1984)] is extended for this purpose. Here the physical system of interest consists of real indistinguishable particles plus one fractional particle, whose potential energy of interaction with the rest of particles is scaled by a coupling parameter, ranging dynamically between zero and one. This coupling changes the number of particles in the system gradually and dynamically, depending on the target values of the excess chemical potential, temperature, and volume. A nonlinear scaling scheme has been adopted to scale the potential energy of interaction of the fractional particle with the rest of the system. The method has been employed to predict the density of compressed Lennard-Jones fluid, compatible with the target values of temperature and the excess chemical potential, over a wide range of temperatures and densities. The method has further been applied to do molecular dynamics simulation in the grand canonical ensemble for water and to predict its vapor-liquid phase coexistence point. The results obtained using this method are in complete agreement with previously reported results in the literature. [ABSTRACT FROM AUTHOR]

In this work, our previous simulation method on the calculation of solubility of nonpolar solutes in nonpolar polymers [H. Eslami and F. Müller-Plathe, Macromolecules 40, 6413 (2007)] has been extended to the case of solubility calculation for water, as a polar penetrant, in poly(ethylene terephthalate), as a polar polymer. The chemical potentials of water in the polymer phase and in the gas phase have been calculated by employing our grand canonical ensemble molecular dynamics simulation method [H. Eslami and F. Müller-Plathe, J. Comput. Chem. 28, 1763 (2007)]. In this paper it is shown that performing just two independent simulations, one in the polymer phase and one in the vapor phase, in the grand canonical ensemble, is sufficient to calculate the phase coexistence point. The calculated solubilities, diffusion coefficients, and permeability coefficients are in good agreement with experimental data. Also the calculated glass transition temperature of the wet polymer is shown to be in a very good agreement with experiment. [ABSTRACT FROM AUTHOR]

A method for the simulation of fluids confined between surfaces is developed. The molecular dynamics, with coupling to an external bath, simulation method of Berendsen et al. [J. Chem. Phys. 81, 3684 (1984)] is extended for this purpose. We keep the temperature and the parallel component of pressure fixed and change the box length in the perpendicular direction with respect to the confining surfaces to archive equilibrium. The simulation is easy to perform, especially in the case of solvation force computation. Employing this method, the simulation results on the confined Lennard-Jones and water are presented and are compared to previous grand canonical ensemble Monte Carlo and molecular dynamics simulation results. While consistent with other methods, our results show that spherical Lennard-Jones particles and water form layered structures parallel to the confining surfaces with enhanced layering with increasing pressure. Also we studied the oscillatory behaviors of solvation force and number density of confined particles as well as the stepwise variation of particle numbers as a function of separation between confining surfaces. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study was to synthesize and characterize novel three-dimensional porous scaffolds made of poly (lactic-co-glycolic acid)/TiO 2 nanotube (TNT) composite microspheres for bone tissue engineering applications. The incorporation of TNT greatly increases mechanical properties of PLGA/TNT microsphere-sintered scaffold. The experimental results exhibit that the PLGA/0.5 wt% TNT scaffold sintered at 100 °C for 3 h showed the best mechanical properties and a proper pore structure for tissue engineering. Biodegradation test ascertained that the weight of both PLGA and PLGA/PLGA/0.5 wt% TiO 2 nanotube composites slightly reduced during the first 4 weeks following immersion in SBF solution. Moreover, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and alkaline phosphatase activity (ALP activity) results represent increased cell viability for PLGA/0.5%TNT composite scaffold in comparison to the control group. In vivo studies show the amount of bone formation for PLGA/TNT was approximately twice of pure PLGA. Vivid histologic images of the newly generated bone on the implants further supported our test results. Eventually, a mathematical model showed that both PLGA and PLGA/TNT scaffolds' mechanical properties follow an exponential trend with time as their degradation occurs. By a three-dimensional finite element model, a more monotonous distribution of stress was present in the scaffold due to the presence of TNT with a reduction in maximum stress on bone. [ABSTRACT FROM AUTHOR]

Objective: The diminished ovarian reserve (DOR) is a condition characterized by a reduction in the number and/or quality of oocytes. This primary infertility disorder is usually accompanied with an increase in the follicle-stimulating hormone (FSH) levels and regular menses. Although there are many factors contributing to the DOR situation, it is likely that many of idiopathic cases have genetic/epigenetic bases. The association between the FMR1 premutation (50-200 CGG repeats) and the premature ovarian failure (POF) suggests that epigenetic disorders of FMR1 can act as a risk factor for the DOR as well. The aim of this study was to analyze the mRNA expression and epigenetic alteration (histone acetylation/methylation) of the FMR1 gene in blood and granulosa cells of 20 infertile women. Materials and Methods: In this case-control study, we analyzed the mRNA expression and epigenetic altration of the FMR1 gene in blood and granulosa cells of 20 infertile women. These women were referred to the Royan Institute, having been clinically diagnosed as DOR patients. Our control group consisted of 20 women with normal antral follicle numbers and serum FSH level. All these women had normal karyotype and no history of genetic disorders. The number of CGG triplet repeats in the exon 1 of the FMR1 gene was analyzed in all samples. Results: Results clearly demonstrated significantly higher expression of the FMR1 gene in blood and granulosa cells of the DOR patients with the FMR1 premutation compared to the control group. In addition, epigenetic marks of histone 3 lysine 9 acetylation (H3K9ac) and di-metylation (H3K9me2) showed significantly higher incorporations in the regulatory regions of the FMR1 gene, including the promoter and the exon 1, whereas tri-metylation (H3K9me3) mark showed no significant difference between two groups. Conclusion: Our data demonstrates, for the first time, the dynamicity of gene expression and histone modification pattern in regulation of FMR1 gene, and implies the key role played by epigenetics in the development of the ovarian function. [ABSTRACT FROM AUTHOR]

A metadynamics scheme is presented in which the free energy surface is filled with progressively adding adaptive biasing potentials, obtained from the accumulated probability distribution of the collective variables. Instead of adding Gaussians with assigned height and width in conventional metadynamics method, here we add a more realistic adaptive biasing potential to the Hamiltonian of the system. The shape of the adaptive biasing potential is adjusted on the fly by sampling over the visited states. As the top of the barrier is approached, the biasing potentials become wider. This decreases the problem of trapping the system in the niches, introduced by the addition of Gaussians of fixed height in metadynamics. Our results for the free energy profiles of three test systems show that this method is more accurate and converges more quickly than the conventional metadynamics, and is quite comparable (in accuracy and convergence rate) with the well-tempered metadynamics method. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Burn wound healing can result in complex problems; therefore, the discovery of an effective method to improve the healing process is vital. Chitosan is applied as a natural biopolymer for wound healing because of its non-toxicity activity, biodegradability, and biocompatibility. Natural metabolites would possibly function like anti-inflammatory and antimicrobial agents and speed up the curing procedure. Using antibacterial wound dressings can efficiently prevent the leftover antibacterial nanomaterials for injection in vivo, thus their biological toxicity to common tissues and cells decreases, causing them to be greatly administered in the biomedical field. The present research intends to evaluate the healing potential of antibacterial guar gum/chitosan/peppermint essential oil hydrogel in the healing of full-thickness burns in a rat model. After creating a complete thickness burn Staphylococcus sp, infected wound on each rat dorsum under general anesthesia, the wound burns were healed with chitosan/guar gum hydrogel; chitosan gel; chitosan/Peppermint hydrogel; chitosan/guar gum/eppermint hydrogel, respectively. Also, the results of the minimum inhibitory concentration of gel for Candida glabrata, Candida Albicans, Escherichia coli and Staphylococcus sp obtained 9.2, 8.3, 7.6, and 5.7 mg/ml respectively. The histopathological and histomorphological observations, including wound contraction, epithelial gap, angiogenesis, the thickness of collagen fibers, fibroblast cells agglomeration, hyperemia, and inflammatory cellular reaction revealed that chitosan/guar gum/peppermint had the best function in the wound healing process (On the 22nd day, the rate of wound contraction was about 90%.) Excellent performance of chitosan/guar gum/Peppermint hydrogel in the healing process provides state-of-the-art knowledge about manufacturing clinical antibacterial wound curing goods. [ABSTRACT FROM AUTHOR]

In this research, TiO2-derived nanotubes were obtained when TiO2nanopowders were treated chemically with NaOH aqueous solution at various reaction temperatures and subsequently, washing with HCl aqueous solution. While increasing temperature, the morphology altered from spherical particles to sheets at 90°C and then to nanotubes when temperature became higher. Therefore, the reaction temperature is a key factor in elucidating the aspect ratio of tubes, whereby specific surface area varied from 66 m2/g for TiO2nanopowders and reached 337 m2/g for synthesized nanotube at 150°C that are expected to have great potentials for biomedical applications. Also, X-ray diffraction results clearly showed the conversion particle to tube of including Na2Ti3O7phase. Electron microscopy micrographs presented the needle-shaped materials with a tubular structure, less than 50 nm in diameter and with length of few hundred nanometers, as well as scroll-like structure and multilayered. Eventually, the 1D prepared structures displayed a remarkable stability during heating and remaining composition even up to 600°C. [ABSTRACT FROM PUBLISHER]

In this article, application of molecular simulation methods for studying molecular pictures of nanoconfined polymers is reviewed and discussed. The simulation methods, covering a range from atomistic to systematically parameterised coarse-grained models, employed in the literature to study nanoconfined polymers are reviewed and their results are compared together. The effect of polymer–surface interactions, surface curvature and surface area on the alteration of polymer structure and dynamics from the unperturbed (bulk) polymer properties are discussed. The length scales over which the surface influences the polymer structure and dynamics and the magnitude of surface effect on dynamics deceleration in the interphase are addressed in terms of different local and global chain properties. [ABSTRACT FROM PUBLISHER]

Molecular dynamics simulations are done to study the structure and dynamics of hydrogen bonds (HBs) in water, nanoconfined between parallel graphene surfaces, at a constant parallel component of pressure, 101.3 kPa, and at constant temperatures, ranging from 300 to 390 K. The results indicate that layering of water molecules beside the surfaces strongly influences the structure of HBs. Very close to the surfaces, due to the geometrical restrictions, the hydrogen atoms of water preferentially orient toward the surfaces, and hence, scarify their HB network. The number of HBs per donor, compared to the corresponding bulk value, is reduced in the organized water layers beside the surfaces. In contrary, their number is increased at distances corresponding to the density profile minima, due to the formation of HBs between donors and acceptors in the neighboring organized layers. An analysis of the temperature dependence of the number of HBs shows that the HBs closer to the surfaces are weaker than those in the bulk water. Besides, the entropy change for HB breakage in the pore is lower than that for the bulk water. The short-time behavior of HB dynamics, with a characteristic time ≈0.1 ps, is shown to be insensitive to the surface proximity. However, an examination of the long-time relaxation of HBs indicates that HBs closer to the surface relax slower than those in the bulk. Such a slower relaxation is shown to be connected to the slower diffusive motion of water, depending on the surface proximity. Consequently, the rate constants for forward (HB breakage) and backward (HB formation) reactions in the pore are smaller than the corresponding bulk values. In all cases, the effect of surfaces is shown to extend up to ≈1.0 nm (interphase thickness) from the surfaces. [ABSTRACT FROM AUTHOR]

Large scale atomistic molecular dynamicssimulation for a nanoparticlein oligomeric poly(methyl methacrylate), composed of 20 repeatingunits, for a long time, up to 100 ns, are performed. Simulations aredone for systems up to 87500 atoms, each containing a single bareor surface-grafted nanoparticle of various diameters and graftingdensities. The effect of surface area, surface curvature, graftingdensity, and hydrogen bonding on the alteration of local structuraland dynamical properties of the polymer is studied in details. Althoughatomistic simulations are only feasible for oligomeric chains in contactwith surfaces, the results of the present simulation still discriminatethe interphase thickness, defined in terms of local and global chainproperties. In the case of structural properties, a minimum interphasethickness, ≈ 2 nm, is associated with local properties suchas layering of individual polymer monomers. However, when probed interms of global chain properties like the extension of chains fromthe interface to the polymer phase, a thicker interphase, three timesthe radius of gyration of the unperturbed chain (Rg≈ 1 nm), is observed. Our resultson the chain structures are shown to be in good agreement with experimentwhere available. An examination of the dynamical properties showsthat the surface influence on the polymer dynamics depends on thelength and time scale of the corresponding bulk property. The changein time scales, in a 0.5 nm thick spherical shell, around the nanoparticle,is shown to cover a broad range from a few tens of a percent (fora short-time dynamical property, like the hydrogen bond formation)to 15–20 orders of magnitude (for a long-time dynamical property,such as the relaxation of end-to-end vector in grafted chains). Therefore,the influence and the range of surface effects on dynamical properties(interphase thickness) depend on the inherent time scale of thoseproperties. In all cases, a thicker interphase is observed for globalstructural and long-time dynamical properties for chains in contactwith a flatter and more densely grafted surface. Hydrogen-bond formationbetween polymer and surface decelerates the polymer dynamics. Theeffect is more pronounced at low temperatures. [ABSTRACT FROM AUTHOR]

Our previously reported modified perturbed hard-sphere-chain equation of state for pure fluids has been extended to mixtures and applied for the prediction ofPVTxproperties of refrigerant mixtures. Generally, two temperature-dependent parameters; an effective van der Waals covolume and a parameter for the strength of the attractive forces between two non-bonded segments, and a third parameter representing the number of chains per molecule appear in the existing perturbed hard-sphere-chain equation of state. It is shown that the critical constants of fluids as input data are sufficient to calculate the temperature-dependent parameters. Our modified equation of state is applied to a variety of liquid refrigerant mixtures over a wide temperature, pressure and concentration range. Comparisons with the experimental data and with the other existing equations of state for the liquid mixtures show that the predicting ability of the present equation of state is quite good. [ABSTRACT FROM AUTHOR]

An analytical equation of state by Song and Mason is developed to calculate thePVTproperties of mercury. The equation of state is based on the statistical-mechanical perturbation theory of hard convex bodies and can be written as a fifth-order polynomial in the density. There exists three temperature-dependent parameters in the equation of state; the second virial coefficient, an effective molecular volume, and a scaling factor for the average contact pair distribution function of hard convex bodies. The temperature-dependant parameters have been calculated using corresponding-states correlations based on the surface tension and the liquid density at the normal boiling point. Employing the present equation of state, we have calculated thePVTproperties of mercury over a wide range of temperatures and pressures. The average absolute deviation for the calculated density of mercury in the saturation and compressed states is 1.09%. [ABSTRACT FROM AUTHOR]

Our recently developed molecular dynamics simulation method forsimulating fluids confined in nanometric pores [Eslami et al. J. Chem. Phys.2008, 129,194702] is employed to simulate nanoconfined polyamide-6,6+water incontact with graphene monolayers. In this work, a number of dry andwet polymer samples, containing 3 and 6 wt % water at 350 K, confinedin pores of different sizes as well as the bulk polymer samples aresimulated. It is shown that both water and polymer molecules formorganized layers beside the surfaces. The effect of nanoconfinementon the hydrogen bonding in the polymer+water system is studied indetail. It is shown that addition of water to the polymer replacesa fraction of looser amide–amide hydrogen bonds with amide–waterones. The distribution of hydrogen bond lengths shows that both thepolymer and water form shorter length hydrogen bonds in the confinedregion compared to the bulk system. The number of hydrogen bonds betweenpolymer and water molecules is shown to depend on the pore size andon the water content. In small pores, water molecules are forced bythe surfaces into the polymer layers and form strong hydrogen bondswith the amide groups, a process that increases the water solubilityof the polymer in small pores. Increasing the water content in largerpores increases the number of hydrogen bonds between water moleculesand causes the formation of big clusters in the central region ofthe pore. In simulations of to 50 ns, it is shown that such big clustersgrow with of time, and hence, phase separate out from the mixture. [ABSTRACT FROM AUTHOR]

Abstract: Molecular dynamics simulations are performed to study the diffusion and permeation of gases, including argon, nitrogen, methane, carbon dioxide, and propane, in polystyrene over a wide range of temperatures. A jumping mechanism is observed for the diffusion of diffusants in polymer. The calculated diffusion coefficients agree well with the experimental data and with the results of former simulation studies. The relation between the diffusion coefficient and the molecular diameter is confirmed by the results. Our calculated results on the temperature-dependence of diffusion coefficients show that for some gases a break is seen, at the glass transition temperature, in the Arrhenius plot of ln (D) versus 1/T, while for some other light gases, argon and nitrogen, the plot is linear over the whole temperature range. We have also calculated the permeability coefficients, using the diffusion coefficients calculated in this work and our recently published solubility coefficients [Eslami and Müller-Plathe, Macromolecules 2007; 40:6413]. Our results show that the calculated permeability coefficients are higher than the experimental data by almost the same trend observed in the solubility calculations, but the ratios of calculated permeabilities are in a very good agreement with experiment. [Copyright &y& Elsevier]

Abstract: In this study, several fluorine-substituted hydroxyapatite ceramics with the general chemical formula Ca5(PO4)3(OH)1− x F x (0≤ x ≤1), where x =0.0 (hydroxyapatite; HA), x =0.68 (fluorhydroxyapatite; FHA) and x =0.97 (fluorapatite; FA) were prepared. The powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), F-selective electrode, atomic absorption spectroscopy (AAS) and EDTA titration analyses. The powders were uniaxially pressed and were formed as a disc shape. Subsequently, sinterability and thermal stability of synthesized powders were compared together. Also the effect simultaneously of fluoride content and temperature were examined on the lattice parameters and crystallites size of the obtained powders. Mechanical properties including hardness, elastic modulus and fracture toughness were measured using indentation. The in vitro dissolution studies of the samples were carried out at osteoclastic resorption conditions. Finally, the biocompatibility and cytotoxicity of the samples were carried out using osteoblast-like cells and L929 cell line, respectively. The obtained results showed that the thermal stability substantially is increased with increase incorporated fluoride into HA structure. Also it was found that the fluoride reduced the lattice parameters and crystallites size of HA. Finally, the in vitro dissolution studies results suggest that the fluoride substitutions in HA offer the ability to prepare HAs with different degrees of solubility. [Copyright &y& Elsevier]

Abstract: A new molecular dynamics simulation technique in the grand canonical ensemble [H. Eslami, F. Müller-Plathe, J. Comput. Chem. 28 (2007) 1763], has been employed to calculate the chemical potentials in the coexisting liquid and vapor phases of pure water, methanol, and acetonitrile. Calculating the chemical potentials in the liquid phase, a new method [J. Vrabec, H. Hasse, Mol. Phys. 100 (2002) 3375], has been employed to calculate the phase coexistence point. In this method just two independent simulations in the grand canonical ensemble are needed to be performed and the molecules are inserted into or deleted from the system in a dynamical way. [Copyright &y& Elsevier]

An extended system Hamiltonian is proposed to perform molecular dynamics (MD) simulation in the grand canonical ensemble. The Hamiltonian is similar to the one proposed by Lynch and Pettitt (Lynch and Pettitt, J Chem Phys 1997, 107, 8594), which consists of the kinetic and potential energies for real and fractional particles as well as the kinetic and potential energy terms for material and heat reservoirs interacting with the system. We perform a nonlinear scaling of the potential energy parameters of the fractional particle, as well as its mass to vary the number of particles dynamically. On the basis of the equations of motion derived from this Hamiltonian, an algorithm has been proposed for MD simulation at constant chemical potential. The algorithm has been tested for the ideal gas, for the Lennard–Jones fluid over a wide range of temperatures and densities, and for water. The results for the low-density Lennard–Jones fluid are compared with the predictions from a truncated virial equation of state. In the case of the dense Lennard–Jones fluid and water our predicted results are compared with the results reported using other available methods for the calculation of the chemical potential. The method is also applied to the case of vapor-liquid coexistence point predictions. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [ABSTRACT FROM AUTHOR]

Abstract: A modified perturbed hard-sphere equation of state has been applied to calculate the liquid density of alkali metal alloys. Two scaling parameters ε and σ are sufficient to calculate the temperature-dependent parameters of equation of state a(T) and b(T) that are universal functions of the reduced temperature. Calculations cover a broad range of temperature from melting point close to critical point. In this work, we have extended the present correlation to mixtures of any number of components. The predicted results for the liquid density of K–Cs and Na–K alloys over the whole range of concentrations are in good agreement with experimental data. From 220 data points examined for molten alloys deviations are within about 5%. [Copyright &y& Elsevier]

Abstract: We have extended our previous work on the equation of state for refrigerants to their mixtures successfully. The temperature-dependent parameters of the equation of state have been calculated using our previous corresponding-states correlation based on the normal boiling point temperature and the liquid density at the normal boiling point. We have applied a simple combining rule for the normal boiling point constants to extend our previously proposed equation of state to mixtures of refrigerants. In this work the liquid densities of a large number of refrigerant mixtures have been calculated and the results are compared both with experimental data and a recent correlation by Nasrifar et al. (1999). The agreement is good. [Copyright &y& Elsevier]

Abstract: Our previously reported modified perturbed hard-sphere-chain equation of state has been employed to calculate the PVT properties of pure halogenated organic compounds. Knowing the critical constants of fluids as well as one adjustable substance-dependent parameter as input data is sufficient for this purpose. We have tested the proposed equation of state against the experimental data for a large number of pure halogenated organic compounds both in saturation and compressed states. Comparison of the calculated results with the experimental data shows that from 734 data points for saturation state and 1450 data points for compressed state the average absolute deviations in calculated densities are 0.51 and 0.61%, respectively. [Copyright &y& Elsevier]

Abstract: A perturbed hard-sphere-chain equation of state has been applied to calculate the liquid density of molten metals. Two temperature-dependent parameters appear in the equation of state, which are universal functions of the reduced temperature, i.e., two scale parameters are sufficient to calculate the temperature-dependent parameters. Generally, the scale parameters can be obtained by fitting of the experimental data. In this work we have calculated the liquid density of nine metals, including alkali metals, mercury, tin, lead, and bismuth, for which accurate experimental data exist in the literature. The calculations cover a broad range of temperatures ranging from melting point close to the critical point and at pressures ranging from the vapor-pressure curve up to pressures as high as 4000 bar. From about 800 data points examined for the aforementioned liquid metals the average absolute deviation compared with experimental data is 1.64%. [Copyright &y& Elsevier]

Abstract: A perturbed hard-sphere equation of state developed previously for liquid alkali metals has been employed to calculate the liquid density of refractory metals over a wide range of temperatures and pressures. Two temperature-dependent parameters appear in the equation of state, which are universal functions of the reduced temperature, i.e., two scale parameters are sufficient to calculate the temperature-dependent parameters, and hence, to predict the equation of state. It is shown that the scale constants correlate with the normal boiling point parameters of metals. Our calculations on the liquid density of tantalum, rhenium, molybdenum, titanium, zirconium, hafnium, and niobium from undercooled temperatures up to several hundred degrees above the boiling point and pressures ranging from 0 up to 200MPa reproduces very accurately the experimental PVT data. [Copyright &y& Elsevier]

Abstract: Our previous corresponding-states correlation for the prediction of the compressed liquid density of pure substances has been extended to mixtures. The correlation requires the values of critical constants, acentric factor, freezing temperature, liquid density at the freezing point, and an adjustable parameter to determine the saturated liquid densities. The mixtures applied with this correlation are liquefied noble gas and inorganic gas mixtures, mixtures of saturated, aromatic, and aliphatic hydrocarbons, refrigerant mixtures, and mixtures of strongly hydrogen-bonded and polar fluids. The predicted results are compared with the well-known corresponding-states liquid densities by Hankinson et al. and with the correlation recently proposed by Nasrifar et al. It is shown that the present correlation works better than both of them. [Copyright &y& Elsevier]

The liquid density of halogenated hydrocarbons has been calculated using an analytical equation of state. The temperature-dependent parameters of the equation of state have been calculated using our previous corresponding-states correlation based on the normal boiling point constants. In this work, it is shown that the equation of state for halogenated paraffins could be expressed in terms of the minimum input information, namely the normal boiling point temperature and the liquid density at the normal boiling point. The equation of state has been employed to calculate the liquid density of a great number of refrigerants both at saturation and compressed states, over a wide range of temperatures and pressures. A comparison of the predicted results with experimental data shows that the agreement is quite good. [Copyright &y& Elsevier]

A modified perturbed hard-sphere-chain equation of state has been employed to calculate the PVT properties of fluids. Generally, two temperature-dependent parameters; an effective van der Waals covolume and the strength of the attractive forces between two nonbonded segments, and a third parameter representing the number of chains per molecule appear in the existing perturbed hard-sphere-chain equations of state. Knowing two scale parameters; depth of minimum in pair potential and the separation distance between segment centers at this minimum, are sufficient to calculate the temperature-dependent parameters. These scale parameters are obtainable by fitting of experimental data. In this work it is shown that using the critical constants of fluids as scale constants would correlate the temperature-dependent parameters of the equation of state with sufficient accuracy. We have tested the predicted equation of state against the experimental data for a large number of fluids including a number of diatomics, polyatomic inorganic molecules, saturated hydrocarbons up to n-C20H42, and a number of olefins and aromatics. The agreement with experiment is quite good. [Copyright &y& Elsevier]

A general equation of state proposed by Parsafar and coworkers for compressed fluids is developed to compressed liquid alkali metals. According to the resulting equation of state p/ρ2 is a linear function of ρ, where p is the pressure and ρ is the molar density. The slope and intercept of the linear equation are linearly temperature-dependent, i.e., by adjusting four temperature-independent parameters one can predict the volumetric behavior of dense molten alkali metals. The equation of state has been employed to calculate the liquid density of compressed alkali metals over a wide range of temperatures, from melting point up to 2000 K, and pressures ranging from saturated vapor pressure to 1000 bar. The agreement of the predicted results with experiment is remarkable. Also the equation of state has been used to calculate densities, isobaric expansivities, and isothermal compressibilities of liquid alkali metals in the saturation state. The linearity of bulk modulus versus pressure, common bulk modulus point, common compression factor point, linear isotherm regularity, and the linearity of inverse isobaric expansivity versus pressure for compressed liquid alkali metals has been checked by utilizing the present equation of state. [Copyright &y& Elsevier]

Applying the previous correlation for the saturated liquid density of metals, we have developed a corresponding-states correlation for the prediction of their compressed liquid densities. The correlation needs the values of the melting and boiling point parameters of metals plus an adjustable parameter, used to predict the saturated liquid densities. In this work, we have shown that by employing the Tait equation together with the previous correlation, for saturated liquid densities, it is possible to develop an accurate method for the prediction of the compressed liquid density of metals. The agreement of the predicted density values with the experimental ones for alkali metals, mercury, bismuth, tin, and lead over a wide range of temperatures, from melting point up to several hundred degrees above the boiling point, and pressures ranging from the vapor pressure up to 4000 bar, is quite good. From 821 data points examined for the aforementioned metals the average absolute deviation for the calculated densities compared with experiment is 0.72%. The correlation is also examined against a number of existing regularities for the liquid phase. [Copyright &y& Elsevier]

A corresponding-states correlation, originally developed by Iglesias-Silave and Hall for the prediction of the saturated liquid densities, has been extended successfully to the compressed state. The Tait equation has been employed for this purpose and its parameters have been correlated to permit accurate prediction of the liquid densities of compressed fluids. The proposed correlation in this work needs the values of the critical constants, the acentric factor, the freezing temperature, the liquid density at the freezing point, and an adjustable parameter used to determine the saturated liquid densities. If the freezing point parameters are not available, another experimentally available low-temperature datum point may be used instead. Utilizing this correlation, we have calculated the liquid density of a large variety of compounds including liquefied noble gases, a number of inorganic diatomic and polyatomic molecules, saturated, aromatic, and aliphatic hydrocarbons, organic acids, alcohols, and refrigerants. The correlation is also compared with the corresponding-states liquid densities by Hankinson et al. and a recent correlation by Nasrifar et al. It is shown that this correlation is superior to both of them. [Copyright &y& Elsevier]

This work is the continuation of the previous ones on the calculation of the second virial coefficient of nonspherical molecules using an accurate Hartree–Fock dispersion individually damped (HFD-ID) potential type as a core potential. The contributions of different terms including electrostatic, induction, and dispersion interactions to the second virial coefficients are calculated using the previously reported auxiliary functions. Following this procedure, we have fitted the well-depth and the position of the minimum in the core potential to calculate the second virial coefficient of N2O, CH4, C2H4, C2H6, and SF6. Our calculations cover the whole range of temperatures reported in the literature and are compared with the large body of experimental data in the literature, and with the previous calculations by Boushehri et al. (1987). The agreement with both experimental data and theoretical calculations is quite good. [Copyright &y& Elsevier]

The transport properties of noble gases and of some other simple fluids including N2, O2, F2, CO, CO2, CH4, CF2Cl2, C2H6, C3H8 and SF6 have been calculated by the modified Enskog theory. The density dependence of the radial distribution function has been evaluated using an analytical equation of state based on the statistical–mechanical perturbation theory. The resultant transport equation of state needs three temperature-dependent parameters, which can be determined by knowing the intermolecular pair potential, plus the zero-density values of the transport coefficients. Using a simple Lennard–Jones (12-6) potential for the calculation of temperature-dependent parameters and the extrapolation of experimental low-density transport coefficient data to the zero-density limit, one can put the transport equation of state in the predictive mode. In this work the thermal conductivity and the viscosity coefficient of the helium-group gases have been calculated over a wide range of temperatures and pressures. A comparison of the calculated and experimental values of the thermal conductivity and the viscosity yields an average absolute deviation of 2.66% for the thermal conductivity and of 3.03% for the viscosity. [Copyright &y& Elsevier]

A corresponding-states correlation for the prediction of the orthobaric liquid density of molten metals has been developed. The correlation is the extension of the recently developed correlation by Iglesias-Silva and Hall, which needs the values of the critical and triple point constants as well as an adjustable parameter. The critical constants are scarce for almost all metals. Our corresponding-states correlation uses the normal boiling and melting point constants plus an adjustable parameter. While the present correlation is simpler in form than the correlation by Iglesias-Silva and Hall, all of its input data are more readily available for almost all metals. In this work, we have applied the present correlation to molten alkali metals, mercury, bismuth, tin, and lead. From about 150 data points for pure liquid metals the average absolute deviation and the maximum deviation are 0.29 and 1.06%, respectively. Also, we have extended the correlation to mixtures of any number of components. The predicted results for the liquid densities of K–Cs and K–Na mixtures over the whole range of concentrations and that of a ternary molten eutectic of K–Na–Cs at temperatures ranging from melting point up to several hundred degrees above the normal boiling point are in excellent agreement with experimental data. From 247 data points examined for molten alloys, the average absolute deviation and the maximum deviation are 0.59 and 1.91%, respectively. [Copyright &y& Elsevier]

In this paper, using Lebanon's capital, Beirut, as a case study, a methodology is proposed to assess the potential for solar photovoltaics (PV) in urban areas incorporating both economic and non-economic factors. Utilizing a rich spatial dataset of solar irradiation augmented with electricity bills at the building level, the cost and benefit of installing rooftop PV systems for each building is estimated. Additionally, incentives and barriers for adopting those systems are investigated using a probabilistic choice model. The results show that Beirut city has a potential for distributed rooftop solar PV to be between 195 and 295 MWp. However, adoption rates are low at 0.49% and 1.23% for residential and commercial buildings, respectively, reflecting the limitation of financial incentives alone to promote the deployment of distributed renewable energy systems in transition economies. The impact of different incentive policy instruments and the role of solar PV in today's economic crisis in Lebanon is analyzed. The biggest impact was achieved through removing (or lowering) electricity tariff subsidy, although this option remains highly constrained by political calculus. We argue that the Lebanese government should fast-track and implement the required legal framework to facilitate and incentivize distributed power generation from renewable sources to promote both green energy and its financial resilience. The proposed modeling framework together with the results obtained in this study will have important implications for energy policy makers in Lebanon and other transition economies. • The potential for distributed rooftop solar energy in Beirut is estimated at the building level. • The effects of economic and non-economic factors on solar PV adoption are analyzed using a probabilistic choice model. • The impacts of various incentive policies and societal factors on promoting PV are investigated with policy implications. • Electricity subsidy removal increases solar PV adoption rates, partly compensating for weak non-financial incentives. • The government should fast-track implementing the legal framework for distributed power generation including PV systems. [ABSTRACT FROM AUTHOR]

Dissipative particle dynamics simulations were performed to investigate the self-assembly of dipalmitoylphosphatidylcholine (DPPC) as a model lipid membrane on the surface of carbon nanotubes (CNTs). The influence of surface curvature of CNTs on self-assembly was investigated by performing simulations on solutions of DPPC in water in contact with CNTs of different diameters: CNT (10, 10), CNT (14, 14), CNT (20, 20), and CNT (34, 34). DPPC solutions with a wide range of concentrations were chosen to allow for formation of lipid structures of various surface densities, ranging from a submonolayer to a well-organized monolayer and a CNT covered with a lipid monolayer immersed in a planar lipid bilayer. Our results are indicative of a sequence of phase-ordering processes for DPPC on the surface of CNTs. At low surface coverages, the majority of hydrocarbon tail groups of DPPC are in contact with the CNT surface. Increasing the surface coverage leads to the formation of hemimicellar aggregates, and at high surface coverages close to the saturation limit, an organized lipid monolayer self-assembles. An examination of the mechanism of self-assembly reveals a two-step mechanism. The first step involves densification of DPPC on the CNT surface. Here, the lipid molecules do not adopt the order of the target phase (lipid monolayer on the CNT surface). In the second step, when the lipid density on the CNT surface is above a threshold value (close to saturation), the lipid molecules reorient themselves to form an organized monolayer around the tube. Here, the DPPC molecules adopt stretched conformations normal to the surface, the end hydrocarbon groups adsorb on the surface, and the head groups occupy the outermost part of the monolayer. The saturation density and the degree of lipid ordering on the CNT surface depend on the surface curvature. The saturation density increases with increased surface curvature, and better-ordered structures are formed on less curved surfaces. [ABSTRACT FROM AUTHOR]

The purpose of this article is to identify the role of media technology development in the economy. In this study, 30 experts in the field of media were used as a sample. The research method is qualitative. Since in this research, there was a need to address the depth of the subject and a deep and comprehensive understanding of media experts, for this reason, the interview method was used. In order for the interviews to have a specific structure, semi-structured interviews have been used. Data were also analyzed through content analysis using maxqda software. In this study, 23 effective factors that determine the positive and negative role of media technologies in the economy were identified, including: information production and increasing economic knowledge, more employment, consumer welfare, reducing economic inequality, reducing political risk, increasing Economic security and efficiency, more control and supervision of people over economic activities, expansion of corporate markets, creation of free online market, innovations and innovations resulting from new technologies increase revenues, increase competition between organizations increase the quality of economic activities, improve and Improving the standards of economic development, public participation in economic activities, expressing people's satisfaction or dissatisfaction with economic activities, spending time on social networks. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed on ionic liquid (IL) 1-n-butyl-3-methylimidazolium methylsulfate. The calculated densities, diffusion coefficients, and electrical conductivities are in very good agreement with the experiment. While the Nernst-Einstein equation largely overestimates the electrical conductivities compared to experiment, its correction for the joint translation of counterions substantially improves its accuracy. Taking into account the role of correlated motions of ions, expressed in terms of the collective mean-squared-displacement, predicts electrical conductivities in close agreement with the experiment. An examination of different dynamical processes shows that three types of motions occur in this IL. Short relaxation times (<1 ps) and low activation energies (≈4 kJ mol-1) are associated with local structural properties such as hydrogen bonding. The second class, such as structural relaxation of hydrogen bonds, has longer relaxation times (a few ten picoseconds) and higher activation energies (≈10 kJ mol-1). The slowest motions (relaxation times of a few ten nanoseconds and activation energies of ≈35 kJ mol-1) belong to the correlated motions of counterions. Ion-pairing, diffusion, and electrical conductivity belong to this third class. Closeness of the relaxation times and activation energies of the third class processes reveal that exchange of counterions in an ion's solvation shell governs the macroscopic dynamic properties of IL. [ABSTRACT FROM AUTHOR]

Selecting appropriate sites for municipal solid waste (MSW) is a challenging problem for urban communities and has economic and environmental implications. This paper proposes a mathematical optimization model to solve the location problem of MSW sites incorporating both push and pull characteristics. Four objective functions comprising health, safety, environmental (HSE), and economic indicators are considered. These objectives are combined into a single objective function using the weighted sum method and the best method is selected based on noise analysis. The parameter uncertainty is incorporated into the model using expert judgments followed by sensitivity analysis to show the effect of the most important parameters. Using the data from a network of 360 population centers in Tehran, the solution for the model is demonstrated. To our knowledge, this is the first study on location optimization of MSW considering combined HSE and economic indicators. The proposed approach is flexible and parsimonious. [ABSTRACT FROM AUTHOR]

Detailed atomistic molecular dynamics simulations are done on the polystyrene oligomers nanoconfined between parallel graphene surfaces at high (400 K) and low temperatures (300 K) and at 101 kPa using a new method, to quantify the surface effect and the temperature influence on a number of structural and dynamical properties of nanoconfined oligomers. Our findings indicate that the surface effect on the alteration in the chain structure at the interface (compared to the structure of the unperturbed chain) and the interphase thickness, determined in this regards, are temperature insensitive. The surface influence on the dynamic deceleration (compared to the dynamics of the unperturbed chain) and the interphase thickness, determined in terms of alteration in chain dynamics, are temperature dependent. The magnitude of temperature-dependency of the dynamic deceleration at the interface depends on the time scale of the dynamical property of interest. Stronger temperature-dependencies are observed for longer-time dynamical properties. [ABSTRACT FROM AUTHOR]

We have constructed efficient coarse-grained (CG) models of poly(ethylene terephthalate) (PET), using three mapping schemes, in which a repeat unit is lumped into either three or four beads. The CG potentials are parameterized to reproduce target distributions of an underlying accurate atomistic model [H. Eslami and F. Müller-Plathe, Macromolecules 42, 8241–8250 (2009)]. The CG simulations allow equilibration of long PET chains at all length scales. The CG results on the density of PET in melt and glassy states, chain dimension, local packing, and structure factor are in good agreement with experiment. We have established a link between the glass transition temperature and the local movements including conformational transitions and mean-square displacements of chain segments. Temperature transferabilities of the three proposed models were studied by comparing CG results on the static and thermodynamic properties of a polymer with atomistic and experimental findings. One of the three CG models has a good degree of transferability, following all inter- and intra-structural rearrangements of the atomistic model, over a broad range of temperature. Furthermore, as a distinct point of strength of CG, over atomistic, simulations, we have examined the dynamics of PET long chains, consisting of 100 repeat units, over a regime where entanglements dominate the dynamics. Performing long-time (550 ns) CG simulations, we have noticed the signature of a crossover from Rouse to reptation dynamics. However, a clear separation between the Rouse and the reptation dynamics needs much longer time simulations, confirming the experimental findings that the crossover to full reptation dynamics is very protracted. [ABSTRACT FROM AUTHOR]

Abstract: A corresponding-states correlation for the prediction of the liquid density of alkali metals has been employed to calculate the liquid density of a wide variety of liquid metals including alkaline earth metals, gallium, indium, thallium, tin, lead, antimony, bismuth, and a number of transition metals. The correlation requires the values of the melting and boiling point parameters of metals plus an adjustable parameter, used to predict the saturated liquid densities. We have calculated the liquid density of above mentioned metals over a wide temperature-range from undercooled temperatures up to several hundred degrees above the boiling point and at pressures from vapor pressure up to 200MPa, where the experimental data are reported in the literature. From 277 data points examined for the afore cited liquid metals the average absolute deviation is 0.386%. [Copyright &y& Elsevier]