Organic Boundary Research Articles

A novel polyvinyl alcohol hydrogel functionalized with organic boundary lubricant for use as low‐friction cartilage substitute: Synthesis, physical/chemical, mechanical, and friction characterization

A novel material design was developed by functionalizing polyvinyl alcohol hydrogel with an organic low-friction boundary lubricant (molar ratios of 0.2, 0.5, and 1.0 moles of lauroyl chloride). The hydrogels were fabricated using two different techniques. First, the boundary lubricant was initially functionalized to the polymer, then the hydrogels were created by physically crosslinking the reacted polymer. Second, hydrogels were initially created by crosslinking pure polyvinyl alcohol, with the functionalization reaction performed on the fully formed gel. After the reaction, Fourier transform infrared spectroscopy and attenuated total reflectance spectra revealed a clear ester peak, the diminishment of the alcohol peak, and the amplification of the alkyl peaks, which confirmed attachment of the hydrocarbon chains to the polymer. Additional chemical characterization occurred through elemental analysis where an average increase of 22% carbon and 40% hydrogen provided further confirmation of attachment. Physical characterization of the boundary lubricant functionalized hydrogels was performed by water content and contact angle measurements. Water content dependency showed that method 1 had a direct relationship with boundary lubricant concentration, and method 2 displayed an inverse relationship. The contact angle increased as boundary lubricant concentration increased for the pure matrix material for both processing methods, suggesting that the hydrocarbons produced surface properties that mimic natural cartilage, and contact behavior of the biphasic system was dependent on processing method. Friction tests demonstrated a significant decrease in friction coefficient, with a maximum decrease of 70% and a minimum decrease of 24% for boundary lubricant functionalized hydrogels compared with nonfunctionalized polyvinyl alcohol hydrogels.

Tribocorrosion reactions between metal-on-metal and metal-on-polymer surfaces for total hip replacement

The open circuit potential and linear polarisation resistance were measured during pin-on-plate tribometer tests for three different total hip replacement bearing material combinations in 0.35% NaCl and bovine serum solutions. In addition, surface analysis was performed using laser interferometry and focused ion beam scanning electron microscopy. It was found that the level of tribologically enhanced corrosion taking place at the bearing surface was substantially higher for metal-on-metal tribocouples than metal-on-polymer ones. Tribological depassivation may be reduced by the presence of organic boundary lubricants.

Redefining the Nation: Shifting Boundaries of the ‘Other’ in Greece and Turkey

While Greek and Turkish nationalisms have followed diverse historical paths, they share several features. Following the model of Zimmer, this study explores how inclusive and exclusive boundary mechanisms have shaped Greek and Turkish national identity and which symbolic resources were utilized in these processes. It is argued that a shift from the use of voluntaristic to that of organic boundary mechanisms has characterized both Greek and Turkish nationalisms and influenced the definition of national ‘self’ and ‘other’. This study aims to track a pattern of historic-political conditions which favour a shift from voluntaristic towards organic models of defining the nation and discuss possible future trends.

The Study of the Dynamic Thickness of Organic Boundary Films Under Metallic Sliding Contact

The paper herein proposes a method to simultaneously measure the friction, wear, and thickness of boundary films under a pure sliding contact between metallic surfaces. The method is based on the capacitance method used by Crook and Dyson et al. to measure elastohydrodynamic film thicknesses. Pilot tests conducted on sunflower oil using the new method showed an appreciable growth in the boundary film thickness, with a corresponding drop in the coefficient of friction. Very little wear was observed during the film growth. It is postulated that this growth was due to the polymerization of the unsaturated fatty acid chains.

Boundary Lubricant - Functionalized PVA Gels for Biotribological Applications

AbstractA novel material design was developed by functionalizing a biocompatible hydrogel material with organic boundary lubricants. Polyvinyl alcohol was functionalized with varying molar ratios of 0.2, 0.5, and 1.0 moles of lauroyl chloride. Tribological and mechanical characterization was performed by means of nanofriction testing and nanoindentation to determine the influence of the hydrocarbon chains on the friction coefficient and elastic modulus of the hydrogels. It was found that fusing of the lubricant to the polymer material has a positive effect on the surface friction properties, yet an unfavorable effect on stiffness properties of the gel due to the processing method.

Quantifying the effect of organic farming, field boundary type and landscape structure on the vegetation of field boundaries

The general aim of the study was to determine the main factors of plant species richness and composition in field boundaries. We surveyed the vegetation of field boundaries in organic and non-organic farms, recorded the field boundary type and width. We characterized landscape structure around the vegetation plots ( r = 250 m). We classified plant species into two ecological response groups: (1) common weeds and other species occurring frequently on agricultural land, i.e. ‘agrotolerant species’ (47 species), and (2) all other species intolerant to contemporary agricultural practices—so-called ‘nature-value species’ (190 species). We analysed the effect of organic farming, boundary type and landscape structure on the diversity of these two species groups. We found that field boundary type and landscape structure described most of the variation in species composition of these boundaries, while organic farming had little effect. However, the analysis of plant species diversity revealed that organic farming significantly supported the species richness of high nature-value species by increasing species richness on average by two species on 4 m 2 plot, while the richness of agrotolerant species did not depend on farming type. Boundary type had a specific impact on species diversity—ditches enhanced the richness of nature-value species and suppressed agrotolerants; woody boundaries hosted only a few agrotolerant species and road verges increased the species richness of both species groups. The richness of nature-value species benefited from wider open boundaries, while narrow boundaries hosted more agrotolerant species.

Selective membrane alternative to the recovery of zinc from hot-dip galvanizing effluents

This work reports the study of the kinetics of zinc recovery from spent pickling solutions by means of emulsion pertraction technology (EPT) in order to reuse the metal in electrolytic processes. Tributyl phosphate (TBP) and service water were used as extraction (EX) and back-extraction (BEX) agents, respectively. Kinetic experiments were carried out in hollow fiber membrane contactors in order to analyse the influence of several operation variables on the rate of zinc recovery. A mathematical model that considers the mass transfer resistance shared between the organic liquid membrane and the organic phase boundary layer was developed; the mass transfer coefficients were estimated by means of the parameter estimation tool ASPEN CUSTOM MODELER (from ASPENTECH) to obtain the values k m = 2.68 × 10 −7 m/s and A V k o = 0.0125 s −1. Simulated results agreed satisfactorily well with experimental data. Consequently, the kinetic model and parameters were confirmed. Finally, a comparison between EPT and non-dispersive solvent extraction (NDSX) was carried out in order to evaluate the advantages and disadvantages of both membrane configurations.

Application of a 3-D chemical fate prediction model (FATE3D) to predict dioxin concentrations in the Tokyo Bay

A 3-D chemical fate prediction model (FATE3D) was applied to predict the dioxin concentrations in the seawater of Tokyo Bay, Japan. The simulations were carried out for a period of one year (from September 2002 to August 2003). Parameters such as meteorological data, flow field conditions, concentrations and sinking rates of organic particulate matter, initial and boundary conditions, and loading fluxes and physico-chemical properties of dioxins were used as the model inputs. The simulation results compared favorably with the field measurements of dioxin concentrations in the bay for both the particulate and dissolved phases, indicating the validity and predictive capability of the model. Furthermore, the differences in the seasonal cycles and distributions between the particulate- and dissolved-phase dioxins in the bay were estimated from the simulation results. However, the particulate-phase dioxin concentrations in the bottom layers (+1 m from the bottom) were underestimated, probably because the resuspension process was not taken into account in the model. The improvement of the model's predictive capability, including the resuspension process, shall be the focus of our next study.

A New Version of the Scintillation Phase Procedure

The scintillation phase procedure based on measuring the counting rate of compounds labeled with tritium in a two-layer scintillation cocktail-aqueous solution system was modified. Previously this procedure was used primarily for studying sorption of proteins at the phase boundary. After certain modification, it became applicable to studying the kinetics of sorption and the equilibrium sorption of various compounds at the organic scintillation cocktail-aqueous solution boundary and to evaluating the distribution coefficients of compounds in this system. Two experimental modes are proposed: common two-layer system and drop system. The suitability of these procedures for determining the surface activity and hydrophobicity of organic compounds and for studying the permeability of the molecular layers adsorbed at the phase boundary is discussed.

Membrane extraction for separation of copper cations from acid solution using polypropylene hollow fibre membrane

The membrane extraction of copper ions was carried out using hydrophobic poly(propylene) (PP) hollow fiber membrane modules and kerosene solutions containing organic extractant. The influences of different extractant on the extraction yield, mass transfer performance and mass transfer mechanism were studied. Compared with 2-ethylhexyl phosphoric acid (2EHPA) and 2-methyl-5-sulpho benzaldoxime (2M5SB), di-(2-ethylhexyl)phosphoric acid (D2EHPA) extractant system with high distribution coefficient exhibited higher extraction yield of 99.7%. The extraction equilibrium time, the final extraction yield and the total mass transfer coefficient were independent of the flow rates of two phases. The extraction equilibrium time and the final extraction yield at different flow rates of two phases were 80 min and near 99.5%, respectively. A mass transfer model of a complexation reaction describing the overall mass transfer resistance was controlled by interfacial reactions rather than the aqueous and organic boundary layer which could explain the effect of flow rate on the final extraction yield and the total mass transfer coefficient. This model showed that the mass transfer resistance and mass transfer coefficient were independent of Cu2+ when copper ion concentration was more than 0.06 g/L. However, when copper concentration was less than 0.06 g/l, the mass transfer resistance increased as Cu2+ concentration decreased, and the mass transfer coefficient decreased as Cu2+ concentration decreased. Extractant entrainment in the aqueous phase and membrane fouling were investigated primarily. It was found that the solvent entrainment could reduce to 10 ppm much lower than 200 ppm of the classic liquid–liquid extraction, and that the cleaning of contaminated membranes was not complete. However, it can be still concluded from this research that the membrane extraction in PP hollow fibre with D2EHPA extractant would be an effective and promising processing means for Cu2+ separation from aqueous solution. Copyright © 2005 John Wiley & Sons, Ltd.

Interface HostGuest Interaction Between Calix[4]pyrrole and Neutral Derivatives of Phenol as the Base for Their Potentiometric Discrimination

AbstractCalix[4]pyrrole liquid membrane electrodes display a potentiometric response towards the neutral form of phenol derivatives. They do not respond towards the corresponding anionic forms. The mechanism of the generation of the potentiometric signal relies on: (1) The creation of supramolecular complex calix[4]pyrrolenitrophenol at the organic/aqueous interface; (2) The increasing of the acidity of OH group from nitrophenol molecules due to formation of hydrogen bond between calix[4]pyrrolenitrophenol at the interface; (3) The dissociation of the OH group from calix[4]pyrrolenitrophenol complex and the ejection of H+ to the aqueous layer adjusted to the membrane organic phase boundary. The sensitivity and selectivity of the calix[4]pyrrole liquid membrane electrodes are governed by the lipophilicity and acidity of the phenolic guests. Also, the affinity to create a hydrogen bond between the host and the target molecule is a parameter which has a strong influence on the phenomena studied.

Experimental and simulation study of neon collision dynamics with a 1-decanethiol monolayer.

A study of the energy accommodation of neon colliding with a crystalline self-assembled 1-decanethiol monolayer adsorbed on Au(111) is presented. The intensity and velocity dependencies of the scattered neon as a function of incident angle and energy were experimentally measured. Scattering calculations show good agreement with these results, which allows us to examine the detailed dynamics of the energy and momentum exchange at the surface. Simulation results show that interaction times are, at most, a few picoseconds. Even for these short times, energy exchange with the surface, both normal and in-plane, is very rapid. An important factor in determining the efficiency of energy exchange is the location at which the neon collides with the highly corrugated and structurally dynamic unit cell. Moreover, our combined experimental and theoretical results confirm that these are truly surface collisions in that neon penetration into the organic boundary layer does not occur, even for the highest incident energies explored, 560 meV.

DECIPHERING METAL ANTIAROMATICITY

ROMATIC COMPOUNDS—STAbilized by 4 n + 2π electrons—were once thought to be purely the domain of organic chemistry. But this organic boundary has become flexible in the past few years as several res...

Spin and lattice configurationsin p‐conjugated organic ferromagnetic polymerwith open boundary condition

AbstractBy employing the extended Su–Schrieffer–Heeger Hamiltonian including on‐site and inter‐site Coulomb repulsions, we investigate the spin and lattice configurations in π‐conjugated organic ferromagnetic polymer under the open boundary condition. The results display that for a certain on‐site Coulomb repulsion, the domain solitons in varying appearances will successively appear along the main chain with increasing of electron–phonon interaction while the spin ones come into view at the side radicals, and, moreover, the inter‐site Coulomb repulsion will exert a great influence on both kinds of solitons.

Three-layer flow membrane system on a microchip for investigation of molecular transport.

A stable three-layer flow system, water/organic solvent/water, has been successfully applied for the first time in a microchannel to get rapid transport through an organic liquid membrane. In the continuous laminar flow region, the analyte (methyl red) was rapidly extracted across the microchannel from the donor to the acceptor phase through the organic solvent phase (cyclohexane). Thermal lens microscopy was used to monitor the process. The thickness of the organic phase, sandwiched by the two aqueous phases, was approximately 64 microm, and it was considered as a thin liquid organic membrane. Permeability studies showed the effects of molecular diffusion, layer thickness, and organic solvent-water partition coefficient on the molecular transport. In the microchip, complete equilibration was achieved in several seconds, in contrast to a conventionally used apparatus, where it takes tens of minutes. The thickness of the organic and aqueous boundary layers was defined as equal to the microchannel dimensions, and the organic solvent-water partition coefficient was determined on a microchip using the liquid/liquid extraction system. Experimental data on molecular transport across the organic membrane were in agreement with the calculated permeability based on the three-compartment water/organic solvent/water model. This kind of experiment can be performed only in a microspace, and the system can be considered as a potential biological membrane for future in vitro study of drug transport.

Basicity of a novel macrocycle containing thiopyrimidine and uracil moieties in various water-organic mixtures

The acid–base behavior of the novel macrocycle, containing thiopyrimidine and uracil moieties 32-trimethyl-23,36-dioxo-15,19-dithio-2,9,13,20,24,31,34,35-octaazatatracyclo [28,3,110,14,120,24]hexatriacontaheptaen-1(34),10(35),11,13,21,30,32 (1) and the acyclic 1,6-bis[4-(N,N-dimethylamino)-6-methylpyrimidinile-2-thio]hexane (2) were studied by potentiometric, UV-Vis, 1H, NMR spectroscopic methods in water–dimethyl sulfoxide (methanol, 1,4-dioxane) solutions and at the interface between water and chloroform phases. The data obtained indicate, that thiopyrimidine nitrogens are the protonation sites of both 1 and 2. The protonation of 2 occurs in one step, while 1 is protonated stepwise in the pH range 9–2.5. The NMR data indicate that the intramolecular interaction between protonated pyrimidine and uracil moieties is the main reason for the stabilization of protonated forms of 1. The protonation constants of 1 were found to be different in various water–organic mixtures, which is in accord with the different 1H NMR spectra of 1 in various solvents. The protonation of 1 at the water–organic phase boundary is effected by the extraction of [1·2H]2+ into the aqueous phase, which can be regarded as a way of obtaining its water -soluble form.

Phase-Boundary Catalysis of Alkene Epoxidation with Aqueous Hydrogen Peroxide Using Amphiphilic Zeolite Particles Loaded with Titanium Oxide

A new heterogeneous catalytic system, phase-boundary catalysis, for epoxidation of alkene with aqueous H2O2 is proposed. Amphiphilic titanium-loaded zeolite particles, a part of the external surface of which was covered with hydrophobic alkyl groups and the rest being left hydrophilic, were prepared by deposition of titanium species from titanium(IV) tetra-2-propoxide and attachment of octadecylsilyl groups from n-octadecyltrichlorosilane (ODS) onto an NaY zeolite powder. Due to their amphiphilicity, the catalyst particles lay at the liquid–liquid phase boundary between upper alkene and lower aqueous phases, and they showed catalytic activity for epoxidation of 1-alkenes (e.g., 1-octene) with aqueous hydrogen peroxide. The phase-boundary catalytic system required neither stirring to make an emulsion nor addition of a cosolvent to make a homogeneous solution to drive the epoxidation. The yield of 1,2-epoxyoctane, a sole oxidation product from 1-octene, strongly depended on the apparent interphase area of the aqueous–organic phase boundary. The amphiphilic catalyst exhibited much higher catalytic activity than that of hydrophilic titanium-loaded NaY, without modification by ODS, or of a hydrophobic catalyst with almost full coverage by the alkyl groups. A similar trend in the activities of these catalysts was also observed when the reaction was carried out with vigorous stirring, in the presence of a cosolvent, or in a water-carbontetrachloride (CCl4) mixture, where the aqueous hydrogen peroxide phase lies above the CCl4 phase. The phase-boundary catalytic system could also be applied to epoxidation of other normal alkenes. Compared with nonporous silica particles, the use of microporous NaY with a relatively large surface area had a beneficial effect, probably due to an increase both in the surface contact between the aqueous and organic layer and in the number of effective active sites of titanium species on its external surface. On the basis of these experimental results, a reaction model is proposed.

Temperature and gate voltage dependent transport across a single organic semiconductor grain boundary

Temperature and gate voltage dependent transport measurements on single grain boundaries in the organic semiconductor sexithiophene (6T) are described. Isolated grain boundaries are formed by vacuum deposition of pairs of 6T grains between Au electrodes 1.5–2.0 μm apart on SiO2/Si substrates; grain boundary formation is monitored using atomic force microscopy. The Si substrate serves as the gate electrode. We show from the activation energy, threshold voltage, and field effect resistance of the grain boundary junction that carrier transport is limited by the grain boundary. The activation energy of room temperature transport is of the order of 100 meV at carrier densities of ∼1018 cm−3 and decreases with increasing carrier concentration (gate voltage). We also observe that longer grain boundaries with smaller misorientation angles result in larger currents through a grain boundary. We relate our data to two models, one that assumes acceptor-like traps localized at a grain boundary and another that assumes localized donor-like traps. Using the activation energy as a measure of the potential well (acceptor model) or barrier (donor model) at a grain boundary, we calculate trap densities of the order of 1012 cm−2 assuming discrete trap energies of 0.015 and 0.34 eV relative to the valence band in the acceptor and donor models, respectively. We note that the calculated values of the trap density are sensitive to the estimated value of the trap level.

A river runs through it: The meaning of the Lesotho‐free state border

This study of Basotho attitudes towards and meanings of the Lesotho‐South African border along the Caledon River valley, next to what is historically known as the Conquered Territory in the eastern Free State, details the long history of struggle and co‐operation between the Basotho and the white inhabitants of the Free State. Analysis of the specific nature of the flow of commodities, trade, labour, and contraband over the Caledon River border bridges during the past ninety years demonstrates that the Caledon is a political rather than an organic social boundary, and that the river itself is the centre of a cross‐border way of life, paradoxically both obstructed and united by ‘international’ border stations. The conflictive history of postindependence Lesotho politics reveals how profoundly attitudes towards and relations with South Africa, and specifically the border communities of the Free State, are implicated in every aspect of the country's national existence. The lack of any effective sovereignty for Lesotho has problematic implications for the maintenance of border controls and restrictions on immigration from Lesotho in the post‐apartheid period. In practice the border posts can operate with neither credible efficiency nor neighbourly openness, because the border is not an international political or economic boundary and control point but rather a business. Political integration of Lesotho into South Africa in some form is seen as inevitable, notwithstanding the desire and efforts of either or both the Lesotho and South African governments to prevent it.What ‘the Basotho’ ultimately want, independence or no independence, is the continuing development of the Caledon Valley's organic multi‐racial way of life. SADC's military intervention in 1998 revealed deep fissures in Lesotho society. Ironically, military intervention to stabilize Lesotho's political situation appears to have accelerated the movement towards eventual incorporation.

Characterization and Modeling of the Extraction Kinetics of Organic Acids Considering Boundary Layer Charge Effects

Characterization and Modeling of the Extraction Kinetics of Organic Acids Considering Boundary Layer Charge Effects