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Accurate prediction of solubility of polymers in solvents a priori is highly desirable in practice. To this end, the Flory-Huggins interaction parameter χ is commonly used and molecular dynamics simulation, a powerful computational tool, has been used for such a purpose. To calculate w, there exist three possible strategies using molecular dynamics simulation. One is through the calculation of Hildebrand solubility parameters of the pure components while the other two are to calculate the enthalpy of solvation and Gibbs free energy of solvation for the solution, respectively. This study evaluated these three strategies using binary solutions containing a hydrophobic or hydrophilic polymer (polyisobutylene, polystyrene, cis and trans polybutadiene, cis and trans polyisoprene, poly(ethylene oxide), and polyacrylamide) and an aliphatic solvent - cyclohexane. We found that χ determined via solubility parameters predicted the solubility trend but deviated significantly from experimental values. On the other hand, the enthalpy of solvation approach provided the most accurate χ values, compared to experiment, at a reasonable computational demand, especially for hydrocarbon polymers, while the Gibbs free energy of solvation approach, though more computationally intensive, did not significantly improve χ from the enthalpy of solvation approach. In particular, the Gibbs free energy of solvation approach overestimated χ for non-polar polymers. A conformational analysis of the solvated polymers revealed that all polymers collapsed in cyclohexane with polyethylene oxide and polyacrylamide collapsed the most as expected. For the two polar polymers used, the collapse was evidenced by abrupt changes in radius of gyration (Rg) and solvent accessible surface area (SASA) in the early stage of molecular dynamics simulation trajectories, and plateauing at much lower final values. Conversely, the hydrocarbon polymers exhibited minimal deviation from the expected Rg and barely any change in SASA with time. Our findings demonstrated that there exist differences in the accuracy and computational resources used when different molecular dynamics simulation strategies are used in the determination of χ. [ABSTRACT FROM AUTHOR]

Rotational diffusion coefficients ( D r ) and viscosities (η) of rigid rod molecules consisting of N beads were first revisited for the situation at low density. Starting from this, the transport coefficients at high density condition were expressed in terms of different density pair correlation functions, such as intermolecular radial distribution function and structure factor. This was attained using a mode-coupling theory approach to approximate the intermolecular force–force correlation function, and thus the friction coefficient. As these density pair correlation functions are dependent on N, they determine how "entangled" the rigid rod molecules are, and therefore reproducing the crossover in the log –log plot of transport coefficients with N. It was found that there are crossovers in transport coefficients from D r ∼ N − 2.3 and η ∼ N 2.3 at low N to D r ∼ N − 6.5 and η ∼ N 6.5 at high N. The strength of N dependence is mainly determined by the competition between available free space and the compressibility of the system. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) is susceptible to environmental stress cracking (ESC). In the presence of an amphiphilic compound and subjected to stress, ESC starts with cavitation followed by slow crack growth and ends with brittle fracture. In this study, we used molecular dynamics simulation to study how branch ends which were chemically modified with vinyl acetate groups affect free volume coalescence around an amphiphilic compound, nonyl ethoxylate (NE), dispersed in branched PE models. Branch ends modified with vinyl acetate significantly impact the free volume coalescence dynamics around NE. Compared with methyl branch ends, vinyl acetate branch ends show a much higher affinity, as quantified by the corresponding radial distribution functions, for the hydrophilic ethylene oxide‐segment of NE. However, this is not the case for the hydrophobic ethylene‐segment. Interestingly, vinyl acetate branch ends tend to reduce the power (amplitude) of the free volume size fluctuations around both the ethylene oxide‐ and ethylene‐segments. Indeed, the powers of the fluctuations with different PE branching characteristics decrease with increasing vinyl acetate concentration. We believe that free volume coalescence leads to cavitation and that vinyl acetate branches could inhibit cavitation, thereby crack propagation in PE. The power results seem to be consistent with the experimental observation that the addition of copolymer ethylene vinyl acetate to low‐density polyethylene improves the ESC resistance of the blend. Highlights: Vinyl acetate branches reduce free volume coalescence activities.Vinyl acetate branches are attracted to the hydrophilic segment of NE.Cavitation likely starts from the free volume coalescence around NE. [ABSTRACT FROM AUTHOR]

Context: To determine the miscibility of liquids at high temperatures using the concept of Hildebrand solubility parameter δ , the current practice is to examine the difference in δ between two liquids at room temperature, assuming that δ is not sensitive to temperature. However, such an assumption may not be valid for certain polymer blends and solutions. Therefore, a knowledge of the δ values of the liquids of interest at high temperatures is desirable. The determination of δ at high temperatures, especially for high-molecular-weight polymers, is impossible, as polymers have vapor pressures of zero. To this end, molecular dynamics (MD) simulations provide a practical means for determining δ over a wide range of temperatures. In this work, we study the temperature dependence of δ of five hydrocarbon polymers: polyethylene (PE), isotactic and atactic polypropylene (i-PP and a-PP), polyisobutylene (PIB), and polyisoprene (PI) in five hydrocarbon solvents: n-pentane, n-hexane, n-dodecane, isobutene, and cyclohexane. The polymers are modeled as monodisperse chains with 100 repeat units. The average δ values of PE, i-PP, a-PP, PIB, and PI at 300 K are determined as 18.6, 14.9, 14.6, 14.3, and 16.4 MPa1/2, respectively, in a good agreement with experimental data. The δ values of these polymers at various temperatures are also determined. The temperature dependence of δ is fitted to two linear equations, one above and the other below the polymer's glass transition temperature Tg. The δ values are more sensitive to temperature at T ≥ Tg. The Tg values of the polymers, determined based upon their specific volumes and δ values agree with the experiment qualitatively. The determination of the temperature dependence of δ has a great potential for industrial applications, such as determining miscibility, developing polymeric organogelators as flocculants and oil spill treating agents, and identifying potential solvents and ideal processing temperatures. Methods: The MD simulations are performed using the GROMACS 2022.3 package with optimized potential for liquid simulations-all atom (OPLS-AA) force field parameters. All polymers are built as extended chains using CHARMM-GUI Polymer Builder. [ABSTRACT FROM AUTHOR]

We used molecular dynamics simulation to study the size distribution and coalescence of free volume around an amphiphilic molecule (nonyl ethoxylate (NE)) at a concentration of 0.5 wt% in blends of linear and branched polyethylene that contained a small four‐arm alkane (7,12 hexyl octadecane). The branched polyethylene chains had 10 and 82 hexyl branches/1000 backbone carbons. The coalescence dynamics (fluctuation of free volume in time) was quantified by the number of Fourier frequencies and the corresponding power (amplitude). In our previous work, we hypothesized that cavitation, the first step of environmental stress cracking observed experimentally, starts from the free volume coalescence at the interface between NE and polyethylene molecules and showed that hexyl branches in the branched polyethylene molecules suppress such coalescence, suggesting that cavitation, a much longer time scale process, could also be slowed down. The current work showed that the behavior of hexyl branches in branched polyethylene in a blend with linear polyethylene was similar to that in pure branched polyethylene, but that the hexyl branches in the 7,12 hexyl octadecane exhibited the opposite behavior. In particular, they intensified free volume coalescence, especially around the hydrophilic ethylene oxide segments of NE. The addition of 7,12 hexyl octadecane to branched polyethylene alone or blended with linear polyethylene does not seem to slow down free volume coalescence (cavitation), leading us to conclude that the effect of hexyl branches on the free volume coalescence around NE depends on the size of the backbone to which the branches are attached. Highlights: Hexyl branches reduce free volume coalescence activities.The longer the backbone is, the stronger the hexyl branch effect.More coalescence activities occur on the hydrophilic segment of NE. [ABSTRACT FROM AUTHOR]

Using a many-chain system of Gaussian chains interacting with each other through the Lennard-Jones (LJ) potential, we demonstrate that there exists a connection between polymer fractional free volume (f) and the entanglement chain length (Ne). Here, f is determined by the generic van der Waals (GvdW) equation of state using the intermolecular radial distribution function [g(r)] of the Gaussian chain generated by the polymer reference interaction sites model while Ne by the polymer mode-coupling theory (PMCT) for strongly coupled macromolecules. The key concept in PMCT is that intermolecular forces experienced by a bead in a chain surrounded by other chains are strongly coupled to the site specific intramolecular radial distribution function. The calculated Gp and η of polyethylene with chain lengths from 500 to 2000 interacting with one another through the LJ potential agree well with experiment and molecular dynamics simulation. [ABSTRACT FROM AUTHOR]

A theoretical method based on the simple Vogel–Fulcher law for estimating the zero shear viscosity of two glass-forming liquids, 1,3-bis(1-nathtyl)-5–(2-naphthyl) benzene and polystyrene, over a range of temperatures from that close to their glass transition temperatures to high temperatures was reported. One parameter of this model, i.e., the critical number density, at which particles are trapped in a cage that only segmental vibration is possible was identified using the intermolecular radial distribution function derived from the Percus–Yevick integral equation and a simplified schematic mode-coupling theory. [ABSTRACT FROM AUTHOR]

We carried out molecular dynamics (MD) simulations on polyethylene (PE) with linear, ring, and four‐arm symmetrical star structures at various molecular weights (420 − 5700 g ⋅ mol−1) and temperatures (410−450 K). We then analyzed the MD data using the technique of proper orthogonal decomposition (POD) to obtain the time correlation functions of different eigenmodes, thereby calculating the viscosity of the aforementioned macromolecules. The time correlation functions show that the ring and star PEs relax much faster than their linear counterpart. Free volume size distributions and the mean fractional free volume of the equilibrated PE melts were determined by Voronoi tessellation (VT). The mean fractional free volume and the corresponding effective pressure were then used to calculate viscosity using a polymer free volume theory recently developed in our lab. The POD and VT approaches yielded similar viscosity values. Furthermore, they both successfully predicted the crossover in the molecular weight dependence of viscosity. It is interesting to note that the difference in the free volume parameters (ϕ+ − F) of various structures always fall within the range of 0.02−0.06. Here, F and ϕ+ signify the probability of a bead having enough free volume for the activation of diffusive motion or momentum transfer and the minimum required fraction of such beads, respectively. The temperature dependence of viscosity as obtained from the POD and VT approaches gave comparable apparent activation energy (Eaapp) values of 5.8−6.4 and 5.4−6.4 kcal ⋅ mol−1, respectively, for the three structures. [ABSTRACT FROM AUTHOR]

Covalent linkages between lignin and the surrounding carbohydrate network, often referred to as lignin–carbohydrate complexes (LCCs), have been proposed to affect the organization of the biomass microstructure and directly correlate with the recalcitrant nature of biomass. However, the existence and frequency of these LCC linkages remain controversial and largely unknown, primarily due to the harsh experimental techniques available to characterize them. During the predominant lignin polymerization pathway a reactive intermediate is formed. Though this intermediate can covalently bind to the surrounding cellulose/hemicellulose matrix, it has been traditionally assumed to react exclusively with water, leading to purely physical interactions between lignin and cellulose/hemicellulose in the cell wall. This work, for the first time, provides direct evidence of the molecular mechanism of the formation of benzyl ether and benzyl ester LCC linkages via the speculated lignin polymerization pathway. The formation of these LCC linkages showed thermodynamic favorability, while remaining kinetically facile, compared to the previously assumed mechanism of the lignin intermediate reacting with water. The present work suggests that the surrounding carbohydrate matrix could play a role in the organization of lignin deposition and these covalent linkages could be a key factor in biomass recalcitrance. [ABSTRACT FROM AUTHOR]

Purpose: To review our institutional experience with the surgical management of prolactinomas through the endoscopic endonasal approach with specific focus on cavernous sinus invasion. Methods: Clinical and radiographic data were collected retrospectively from the electronic medical record of 78 consecutive patients with prolactinomas undergoing endoscopic endonasal resection from 2002 to 2019. Immediate and late post-operative remission were defined as prolactin < 20 ng/mL within 14 days and 1-year of surgery without adjuvant therapy, respectively. Cavernous sinus invasion was quantified by Knosp score. Results: A total of 78 patients with prolactinoma, 59% being male, underwent surgical resection with a mean age of 37 ± 13 years. Indications for surgery were medication resistance in 38 patients (48.7%), medication intolerance in 11 (14.1%), and patient preference in 29 (37.2%). Patients with Knosp 0–2 achieved higher immediate remission rates (83.8%) compared to patients with Knosp 3 (58.8%) and Knosp 4 (41.7%) patients (p = 0.003). Long-term remission rates were 48.7% and increased to 71.8% when combined with adjuvant treatments. Knosp 4 prolactinomas had significantly higher tumor volumes, higher preoperative prolactin levels, higher recurrence rates, higher rates of adjuvant therapy utilization, and were more likely to have failed dopamine agonist therapy compared to other tumor grades (p < 0.05). We encountered 18 complications in our series, and no cerebrospinal fluid leaks. Conclusion: The endoscopic endonasal approach is a safe and effective modality that can be employed in properly selected patients with invasive prolactinomas. It is associated with improved control and remission rates despite cavernous sinus invasion, though at a lower rate than without invasion. [ABSTRACT FROM AUTHOR]

The drying of residue cyclohexane in a series of reconstituted gangue samples at ambient conditions was studied. The reconstituted gangue samples contained controlled amounts of residual bitumen, water, and fines (solid particles <45 μm). Regardless of the gangue composition, the initial drying flux was constant, and more than 90% of the residual cyclohexane was removed in this stage. The initial drying was driven by the liquid film flow induced by the differences in liquid film's radii of curvature along the pore channels. The liquid was a diluted bitumen solution that was transported to the surface, where cyclohexane evaporated with a rate comparable to that of pure cyclohexane evaporation. Upon the solvent evaporation, the dissolved bitumen was deposited on the sample surface. The residual bitumen content exerted an adverse effect on the initial drying flux because the dissolved bitumen significantly increased the solution viscosity, thereby reducing the liquid film flow rate. There existed an optimum water content range (3.9‐6.0 wt%) that facilitated the formation of bitumen solution film in the pores, favouring drying. When there was a high concentration of water or no water, the initial drying flux was decreased remarkably. The initial drying flux was insensitive to the fines content. Adding fines may have two counteracting effects on the drying process. Fines decreased the mean pore size, thereby lowering the liquid film flow rate. However, the hydrophobicity of the pore surfaces was increased as fines are usually covered by asphaltenes. This favours liquid film formation. [ABSTRACT FROM AUTHOR]

The cover image is based on the Research Article Effect of hexyl‐branched backbone size on the size distribution and coalescence of free volume around an amphiphilic molecule by Sajjad Kavyani et al., https://doi.org/10.1002/pen.26705. [ABSTRACT FROM AUTHOR]

Relaxation dynamics of unentangled polymer melts (with a chain length below N = 100 for polyethylene) can be studied by performing either Rouse mode or relaxation mode analysis, such as proper orthogonal decomposition. The former mode analysis can be derived analytically from the linear equation of motion of polymers with the inclusion of inertia term, whereas the latter is designed for the case when the numerical solution to a highly nonlinear equation of motion is known, such as MD simulation data. This article presents a summary of both approaches and their applications in the evaluation of zero-shear viscosity of polymer melts. [ABSTRACT FROM AUTHOR]

Australia and New Zealand have achieved excellent community control of COVID‐19 infection. In light of the imminent COVID‐19 vaccination roll out in both countries, representatives from the Haematology Society of Australia and New Zealand and infectious diseases specialists have collaborated on this consensus position statement regarding COVID‐19 vaccination in patients with haematological disorders. It is our recommendation that patients with haematological malignancies, and some benign haematological disorders, should have expedited access to high‐efficacy COVID‐19 vaccines, given that these patients are at high risk of morbidity and mortality from COVID‐19 infection. Vaccination should not replace other public health measures in these patients, given that the effectiveness of COVID‐19 vaccination, specifically in patients with haematological malignancies, is not known. Given the limited available data, prospective collection of safety and efficacy data of COVID‐19 vaccination in this patient group is a priority. [ABSTRACT FROM AUTHOR]

Understanding stress variations in pulsating flows due to periodic pressure gradients is fundamentally significant for the design and optimization of various medical apparatuses and for understanding biological phenomena. Oscillating flows have been dealt analytically and experimentally in great detail in the past. In this paper, a three-dimensional lattice boltzmann model is used to simulate the pulsating flows in a rectangular duct due to low, moderate, and high periodic pressure gradients. Asymptotic forms for velocity (valid for high frequencies) valid in different regions of the channel have been matched with the analytical results. The evolution of annular effects in the flow along with the Stokesian layer characteristics have been followed. Stress analysis at different points of the wall of the duct has been carried out to show regions of high stress and stress rates. [ABSTRACT FROM AUTHOR]

Steady state pressure driven flow of liquid argon through a finite length cylindrical nanopore was investigated numerically by classical Navier-Stokes (NS) hydrodynamic models and nonequilibrium molecular dynamics (MD) simulations. In both approaches, the nanopore was nominally 2.2 nm in diameter and 6 nm long. For the MD simulations, the intermolecular properties of the walls were specified independently from the liquid. Comparisons between the approaches were made in terms of the gross feature of total flow rate through the nanopore, as well as the more refined considerations of the spatial distributions of pressure, density, and velocity. The results showed that for the NS equations to predict the same trends in total flow rate with increasing pressure difference as the MD simulation, submodels for variations in density and viscosity with pressure are needed to be included. The classical NS boundary conditions quantitatively agreed with the flow rate predictions from MD simulations only under the condition of having a neutral-like solid-liquid interaction. Under these conditions, the NS and MD models also agreed well in streamwise distributions of pressure, density, and velocity, but not in the radial direction. [ABSTRACT FROM AUTHOR]

Fluid transport through a nanopore in a membrane was investigated by using a novel molecular dynamics approach proposed in this study. The advantages of this method, relative to dual-control-volume grand-canonical molecular dynamics method, are that it eliminates disruptions to the system dynamics that are normally created by inserting or deleting particles from control volumes, and that it functions well for dense systems due to the number of particles being fixed in the system. Using the proposed method, we examined liquid argon transport through a nanopore by performing nonequilibrium molecular dynamics (NEMD) simulations under different back pressures. Validation of the code was performed by comparing simulation results to published experimental data obtained under equilibrium conditions. NEMD results show that constant pressure difference across the membrane was readily achieved. [ABSTRACT FROM AUTHOR]

For a model system of polyethylene of chain lengths 40 and 100 carbon atoms, we calculated the pressure at different densities and compared them with the experimental values. The simulation was conducted on the second nearest neighbor diamond lattice, and the pressure was calculated using the virtual-volume-variation method after the system was reverse mapped to its fully atomistic form in continuous space and energy minimized. In addition, the pressure was also calculated from the virial route by conducting a short molecular dynamics simulation starting from the energy minimized structure. We show that the pressure obtained from our simulations is quite reasonable in the length of simulation time (in Monte Carlo steps) normally employed in our group. These results provide additional evidence for the equilibration of our model systems, and methodology to calculate the pressure in our lattice models. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An amorphous 50/50 atactic polypropylene (aPP)/isotactic polypropylene (iPP) mixture at 125 °C was simulated using a second nearest neighbor diamond lattice and a three states rotational isometric state model. The result suggests that at the liquidlike density that corresponds to the atmospheric pressure, aPP prefers to interact with other aPP chains rather than with iPP chains. The result is consistent with the inference of Keith and Padden [J. Appl. Phys. 35, 1286 (1964)] that aPP and iPP will tend to separate from one another in their melt at 125 °C, before the onset of crystallization of iPP. The tendency for immiscibility of the amorphous aPP/iPP blend is likely attributed to the presence of short syndiotactic sequences in the aPP chains adopting all-trans conformations. The attractive intermolecular interaction of pairs of such subchains at 125 °C promotes the separation of aPP from iPP. This interaction is weakened at higher temperature, where aPP and iPP become miscible. The result also shows that miscibility of the blend increases with increasing pressure. However, the origin of the pressure effect is not clear. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations using a modified Drieding 2.21 force field were carried out to study the coalescence behavior of nanometer-sized water droplets in vacuum and in n-heptane. The coalescence mechanisms of the water droplets in the above-noted environments are fairly similar in a sense that the water droplets form a bridge linking the droplets before they merge. However, in the latter situation, due to the presence of n-heptane molecules in between the water droplets, the coalescence was observed to be slowed down considerably, especially in the first 10 ps of the process. However, once the bridge is formed, the water droplets, in both situations, spend about the same amount of time to form a single droplet. The maximum distance between the droplets above which coalescence does not occur was found to be 10 Å. In terms of the dynamics, the diffusion coefficient of n-heptane in the emulsion system was very close to its value in the pure liquid form. This may be because n-heptane is the continuous phase. Nonetheless, the dynamic behavior of water in n-heptane is different from that of pure water during and after the coalescence. In particular, the self-diffusion coefficient of water molecules in n-heptane is about 20% higher than the experimental value of pure water. Due to the lack of strong attraction forces between water and n-heptane molecules, the n-heptane molecules were observed to orient themselves perpendicularly to the water/n-heptane interfaces so that the contacting area is minimized. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation was used to study the adsorption behavior of inorganic and organic ions at aqueous–cyclohexane interfaces, and that with such systems confined in a kaolinite nanopore. Four aqueous solutions were used, each containing one of the four solutes (NaCl, NaOH, CaCl2 and Ca(OH)2) at the concentration of 1.0 M. At the interface of each of the solutions with neat cyclohexane, there existed an ion depletion zone. The more strongly hydrated ions, such as calcium and hydroxide, were more intensely depleted from the interface as compared to sodium and chloride. Such surface exclusion led to interfacial tension increases, with greater increments for solutions containing calcium or hydroxide. Upon addition of sodium decanoate to the cyclohexane phase, they partly migrated to the aqueous–organic interface, and the remaining formed inverted micelle complexes. Also, a small fraction of the solvated cations in the aqueous phase drifted to the depletion zone to interact with the organic anions, with their affinity towards the interface still being controlled by their hydration-strength. When such systems were confined in a kaolinite nanopore, behavior of decanoate anions – which were found to be prone to strong adsorption to solid surfaces in the absence of any aqueous solution – was determined by the nature of the solvated ions in water. In these systems, the more weakly-hydrated ionic species exhibited preferential adsorption to the solid surface, while affinity of the more strongly-hydrated ones was towards remaining within the water layers or to the aqueous–organic interface. With the calcium chloride solution, almost all of the organic ions were detached from the surface and adsorbed at the aqueous–cyclohexane interface. This was caused by the release of double amount of inorganic anions by this 1 : 2 salt, the inner-sphere adsorption of majority of chloride anions to the octahedral surface, and the higher charge density of calcium cations. [ABSTRACT FROM AUTHOR]

Froth flotation has been widely used to separate sulfide minerals from sulfide ores, where the oxygen reduction reaction (ORR) plays a significant role as the cathodic reaction. However, the intrinsic ORR mechanism over sulfide minerals and its effect on the flotation performance remain unclear. Herein, we explored the intrinsic ORR mechanism over metal sulfides through density functional theory (DFT) calculations along with the computational hydrogen electrode (CHE) model. Our results revealed that pyrite (FeS2) and chalcopyrite (CuFeS2) exhibited similar ORR behavior to that over platinum (Pt) but not galena (PbS) and sphalerite (ZnS). The relative computational overpotentials for the ORR were completely consistent with the experimental trend in the order of Pt ＜ FeS2 ＜ CuFeS2 ＜ PbS ＜ ZnS and linearly correlate with the oxygen binding energies. We thus conclude that the distinct ORR behaviors originate from the different oxygen binding strengths which are determined by the underlying electronic structure. More importantly, we demonstrated that the DFT calculated bulk centroids of the occupied S 3p band for metal sulfides strongly correlate with the experimentally measured rest potential of the counter sulfide minerals in xanthate solution, and consequently we established the descriptor–activity relationship. Using this relationship, we present that the mechanism underlying the mixed potential model regarding the xanthate–sulfide mineral interaction is essentially governed by the relative dominating role of the compositional metallic cation to the anionic sulfur in terms of the electronic structure around the Fermi level, which favors the formation of dixanthogen and metal-xanthate, respectively. [ABSTRACT FROM AUTHOR]

Isothermal-isobaric molecular dynamics simulation was used to study the diffusion mechanism of water in polyurethane- block-poly(N-isopropyl acrylamide) (PU- block-PNIPAm) with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature ( T ) of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU-block-PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures (250 K and 390 K) of PU- block-PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures (i.e., following the free volume model of Fujita). It suggested that water diffusion in PU- block-PNIPAm depends only on its fractional free volume despite the free volume inhomogeneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2-0.4 nm in PU- block-PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules. [ABSTRACT FROM AUTHOR]

Solvent-based extraction has the potential to give higher bitumen recovery from mined oil sands without further accumulation of tailings ponds. A crucial aspect of this technology is the recovery of solvent from the solid waste stream, or gangue. Experiments were performed on gangue after cyclohexane extraction from high- and low-grade oil sand ores to determine the effects of drying temperatures from 25 to 105 °C and pressures from 30 to 95 kPa. Increasing temperature and decreasing pressure both increased the mass flux of evaporating cyclohexane. The maximum mass flux of cyclohexane correlated strongly with cyclohexane vapour pressure at the oven temperature. The total time required to reach a target residual cyclohexane concentration of 250 mg/kg followed a power law relationship with both temperature and pressure, ranging from 300 to 9000 s depending on oven temperature and pressure. Evaporation of solvent was slower from the gangue from low-grade ore, with a total completion time 3.2 ± 0.9 (n = 33) times longer compared to gangue from high-grade ore at the same temperature and pressure. The higher water and fines contents of the gangue from low-grade ore likely contributed to this result. [ABSTRACT FROM AUTHOR]

This paper describes a novel method to address the oil sands tailings reclamation problem using surface geopolymerization reactions. Geopolymerization involves dissolution of aluminosilicate minerals and re-solidification reactions that result in the formation of three-dimensional inorganic polymers of significant strengths. Since the fines present in oil sands mature fine tailings (MFT) mainly consist of aluminosilicate minerals, or clay minerals, it is hypothesized that by adding appropriate reagents, the surface of the clay minerals can be activated and go through geopolymerization reaction under ambient conditions. The resulting geopolymeric species formed on the clay minerals will bind the clay particles together and strengthen the tailings even without further dewatering. Geopolymerization was tested on 0.51 g/g (51 wt%) solids centrifuged MFT and its shear strength was observed to increase from 115 to 4880 Pa in 90 days when treated with 40 kg of sodium hydroxide and 60 kg sodium silicate per tonne of dry MFT solids. Similarly, the shear strength of 0.48 g/g (48 wt%) solids polymer flocculated MFT increased from 395 to 3950 Pa 90 days after the addition of the same dosages of sodium hydroxide and sodium silicate. Tests conducted on a geopolymerized model kaolinite sample showed that under the test conditions, the geopolymerization reaction only occurs on the surface of the kaolinite at the indicated dosages. The surface geopolymers held the kaolinite particles together, leading to an increase in its shear strength. [ABSTRACT FROM AUTHOR]

The current production of wood composites relies mostly on formaldehyde-based adhesives such as urea formaldehyde (UF) and phenol formaldehyde (PF) resins. As these resins are produced from non-renewable resources, and there are some ongoing issues with possible health hazard due to formaldehyde emission from such products, the purpose of this research was to develop a formaldehyde-free plywood adhesive utilizing waste protein as a renewable feedstock. The feedstock for this work was specified risk material (SRM), which is currently being disposed of either by incineration or by landfilling. In this report, we describe a technology for utilization of SRM for the development of an environmentally friendly plywood adhesive. SRM was thermally hydrolyzed using a Canadian government-approved protocol, and the peptides were recovered from the hydrolyzate. The recovered peptides were chemically crosslinked with polyamidoamine-epichlorohydrin (PAE) resin to develop an adhesive system for bonding of plywood specimens. The effects of crosslinking time, peptides/crosslinking agent ratio, and temperature of hot pressing of plywood specimens on the strength of formulated adhesives were investigated. Formulations containing as much as 78% (wt/wt) peptides met the ASTM (American Society for Testing and Materials) specifications of minimum dry and soaked shear strength requirement for UF resin type adhesives. Under the optimum conditions tested, the peptides-PAE resin-based formulations resulted in plywood specimens having comparable dry as well as soaked shear strength to that of commercial PF resin. [ABSTRACT FROM AUTHOR]

Solvent extraction of bitumen from the Alberta oil sands has the potential to overcome the shortcomings of the current aqueous extraction process by reducing fresh water demand and eliminating tailings ponds. Bitumen is recovered as a solution, leaving behind the solids (or gangue) with a residual solvent and water from the original ore. Removing the solvent from the gangue is a crucial step that involves evaporation of volatile material (cyclohexane) from a porous matrix in the presence of a less volatile immiscible phase (water). In this study, we examined the effects of relative humidity, temperature, and the addition of water during cyclohexane extraction on the extent of cyclohexane removal from the extraction gangue. The drying curves showed two constant-rate periods, with the initial period mainly removing cyclohexane, and the second mainly removing water. The initial drying rate of gangue in an environmental chamber was 2.7 times faster than drying in a fume hood due to the stronger convective currents in the chamber produced by its fan. The initial drying rate was independent of the relative humidity, which was in the range of 30-90 %, but the residual cyclohexane content in the gangue increased at high relative humidity. The addition of water to oil sands prior to cyclohexane extraction increased the residual cyclohexane in the gangue, likely by forming a barrier to efficient evaporation. [ABSTRACT FROM AUTHOR]

ABSTRACT The sorption of solvents from the vapour phase to solid substrates is important in producing heavy oil and bitumen, particularly from the oil sands. We investigated the sorption and desorption equilibrium and kinetics of cyclohexane, toluene, and water on kaolinite, fine solids, and organic-rich fine solids isolated from Athabasca oil sands over a wide range of solvent vapour concentrations using a gravimetric method. The isotherms for both adsorption and desorption of solvent vapour were determined, and the Brunauer-Emmett-Teller equation was used to fit the experimental data. The initial kinetic rate constants for the adsorption and desorption of solvent vapour were determined with the linear driving force model. The results were compared and discussed in terms of the type of solvent, the content of organic materials, and the surface area of the solid substrates. The results suggest that, in addition to the adsorption of solvent on mineral surfaces, the contribution from solvent partitioning in the organic materials and the porosity resulting from high amounts of organic materials are significant factors for solvent uptake and kinetic rate constants. In mixed solvent vapours, the competitive sorption of water and cyclohexane was observed in the solid substrates. However, the degree of competitiveness decreased with an increase in the content of organic materials in the substrates. [ABSTRACT FROM AUTHOR]

Background: Treatment of low-pressure hydrocephalus (LPH) may require prolonged external ventricular drainage (EVD) at sub-zero pressures to reverse ventriculomegaly. Endoscopic third ventriculostomy (ETV) has been used in the treatment of noncommunicating hydrocephalus; however, indications for ETV are expanding. Methods: Patients with the diagnosis of LPH as defined by the Pang and Altschuler criteria who underwent sub-zero drainage treatment over an 8-year period were included. Patients were divided into two cohorts based on whether or not ETV was employed during their treatment. Time from EVD placement to internalization of shunt was recorded for both groups; time from ETV to placement of shunt was recorded for the patients undergoing ETV. Results: Sixteen adult patients with LPH were managed with sub-zero drainage method. Ten (62.5%) patients did not undergo ETV and the average time from first ventriculostomy to shunting was 73 days (range 14-257 days). Six (37.5%) patients underwent ETV during the course of their treatment; average time from initial ventriculostomy to shunt was 114 days (range 0-236 days) (P = 0.16). Time from development of LPH to ETV ranged from 28 days to 6.5 months. In the ETV group, of the 4 patients who underwent shunting, the average time to shunting following ETV was 15.25 days. Conclusions: ETV can be used successfully in the management of refractory LPH to decrease the duration of EVD. [ABSTRACT FROM AUTHOR]

The article presents a study on the Exoseal vascular closure device (VCD) and its potential in delaying angiographic femoral artery complications. It highlights its application for the closure of femoral arterial puncture as well as attainment of hemostasis. It also notes the nonexistence of angiographic irregularities with its usage which is only seen in 6.86% of cases.

BACKGROUND As a result of the bovine spongiform encephalopathy ( BSE) emergence, certain tissues of cattle are categorized as specified risk material ( SRM) and completely banned from their traditional applications as an ingredient in animal feed, pet food, or fertilizer applications. The goal of this study was to investigate the hydrolysis of such hazardous proteinacious biomass and extract a safe proteinacious fraction to produce industrial feedstock for value-added applications. RESULTS The SRM was hydrolyzed at subcritical temperatures of 180, 200, 220, 240, and 260 °C for 40 min according to government-approved protocols. The recovery and cleavage of proteins and lipids, the generation and degradation of free and total amino acids, and the generation of organic acids were studied and found to be temperature-dependent. The yield of the hydrolyzed and recovered proteinacious fractions varied between 71.6 and 87.6% by weight of the original protein content in the SRM. The molecular size was also significantly dependent on the hydrolysis temperature. CONCLUSION The valorization of an otherwise waste SRM by subcritical hydrolysis and recovery techniques resulted in protein hydrolyzates suitable for bio-based chemicals and materials applications. The increase of temperature resulted in higher degrees of hydrolysis as shown by the smaller molecular size of hydrolyzed proteins. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

It is well-known that properties of poly(vinyl alcohol) (PVA) in the pure and solution states depend largely on the hydrogen bonding networks formed. In the context of molecular simulation, such networks are handled through the Coulombic interactions. Therefore, a good set of partial atom charges (PACs) for simulations involving PVA is highly desirable. In this work, we calculated the PACs for PVA using a few commonly used population analysis schemes with a hope to identify an accurate set of PACs for PVA monomers. To evaluate the quality of the calculated parameters, we have benchmarked their predictions for free energy of solvation (FES) in selected solvents by molecular dynamics simulations against the ab initio calculated values. Selected solvents were water, ethanol and benzene as they covered a range of size and polarity. Also, PVA with different tacticities were used to capture their effect on the calculated FESs. Based on our results, neither PACs nor FESs are affected by the chain tacticity. While PACs predicted by the Merz-Singh-Kollman scheme were close to original values in the OPLS-AA force field in way that no significant difference in properties of pure PVA was observed, free energy of solvation calculated using such PACs showed greater agreement with ab initio calculated values than those calculated by OPLS-AA (and all other schemes used in this work) in all three solvents considered. [ABSTRACT FROM AUTHOR]

The primary goal of this research was to develop a waste protein based adhesive, and to optimize its lap shear strength under dry and wet conditions using Taguchi method. The feedstock for this work was specified risk material (SRM) that is considered the tissue potentially at risk of containing misfolded prions. SRM was hydrolyzed in accordance with government approved techniques and modified with a resin system to develop a renewable adhesive platform. Eight of the nine formulated adhesives met the minimum dry shear strength requirement of urea formaldehyde type adhesive, and three of the formulations also met the soak shear strength requirement. This work demonstrates a general valorization platform for the utilization of animal waste protein as a renewable adhesive feedstock. [ABSTRACT FROM AUTHOR]

Delayed toxicity after whole brain radiation therapy (WBRT) is of increasing concern in patients who survive more than one year with brain metastases from breast cancer. Radiation-related white matter toxicity is detected by magnetic resonance imaging (MRI) and has been correlated with neurocognitive dysfunction. This study assessed the risk of developing white matter changes (WMC) in breast cancer patients who underwent either WBRT plus stereotactic radiosurgery (SRS) or SRS alone. We retrospectively compared 35 patients with breast cancer brain metastases who received WBRT and SRS to 30 patients who only received SRS. All patients had evaluable imaging at a median of one year after their initial management. The development of white matter T2 prolongation as detected by T2 or FLAIR imaging was graded: grade 1 = little or no white matter T2 hyperintensity; grade 2 = limited periventricular hyperintensity; and grade 3 = diffuse white matter hyperintensity. After WBRT plus SRS, patients demonstrated a significantly higher incidence of WMC ( p < 0.0001). After one year, 71.5 % of patients whose treatment included WBRT demonstrated WMC (42.9 % grade 2; 28.6 % grade 3). Only one patient receiving only SRS developed WMC. In long-term survivors of breast cancer, the risk of WMC was significantly reduced when SRS alone was used for management. Further prospective studies are necessary to determine how these findings correlate with neurocognitive toxicity. WBRT usage as initial management of limited brain disease should be replaced by SRS alone to reduce the risk of delayed white matter toxicity. [ABSTRACT FROM AUTHOR]

The primary goal of this work was to develop a novel adhesive technology platform for oriented strand board (OSB) using waste animal protein extracts, as feedstock. In this research, a hazardous animal processing waste was thermally hydrolyzed, and the proteinaceous fractions were recovered and modified into an adhesive. The adhesive developed as such was formulated for OSB adhesion applications, and the OSB performance was also evaluated. Performance results showed that the OSB specimens made with up to 60% by weight of protein hydrolyzate based adhesive met the Canadian Standard Association (CSA O437.0-93) requirements for commercial applications. Based on the intermediate moisture resistance results observed, the recommended use of these boards could be for relatively low moisture environments. [ABSTRACT FROM AUTHOR]

Dynamic Monte Carlo (DMC) simulation was used to study the dynamics of a series of coarse-grained atactic polypropylene ( aPP) model chains (CH) in the melt state at 473 K. Model chains with meso diads factions, P, set at 0.25, 0.5, and 0.75 but with different meso and racemo diads sequences were studied. It was observed that aPP chains with an alternate meso and racemo diads sequence exhibited the highest mobility (or diffusivity) among all stereochemical sequences studied. Additionally, chains with long consecutive sequences of diads of the same type exhibited lower mobility than those with more random stereochemical sequences. The differences in the intramolecular and intermolecular interactions resulting from differences in diad sequences contributed to the observed differences in dynamics. In particular, intramolecular interactions play a more dominant role for aPP chains containing low fractions of meso diads or none at all ( i.e., all racemo diads ( P=0.0) or syndiotactic chains). On the other hand, in the cases of P values close to 1.0 ( i.e., isotactic chains), intermolecular interactions play a more dominant role than the intramolecular interactions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In response to the bovine spongiform encephalopathy (BSE) outbreak in the last decade, the US, Canada and several other countries implemented an enhanced feed ban that eliminates specified risk material (SRM) from all animal feed, pet foods and fertilizer applications. The environmental risks and severe loss of profitability by the rendering industry associated with landfilling of several million tons of SRM demand immediate and economically viable solutions of converting such materials into value added applications. In this research, SRM was hydrolyzed, the protein hydrolyzates were extracted and further modified through chemical crosslinking to develop a novel protein-based plastics. The plastics developed in this research exhibited promising thermal and solvent resistance, and tensile strength. [ABSTRACT FROM AUTHOR]