1,1,3,3-Tetraethylisoindolin-2-ium chloride

In the structure of the title compound C16H26N+ Cl-, the salt of a precursor in the synthesis of an isoindolin-2-yloxyl free-radical trapping agent, the cations and anions form discrete centrosymetric cyclic dimers through N---H...Cl hydrogen-bonding associations [graph set R2/4(8)].

Gold coating of silica and zinc oxide nanoparticles by the surface reduction of gold(I) chloride

The possibility of a surface inner sphere electron transfer mechanism leading to the coating of gold via the surface reduction of gold(I) chloride on metal and semi-metal oxide nanoparticles was investigated. Silica and zinc oxide nanoparticles are known to have very different surface chemistry, potentially leading to a new class of gold coated nanoparticles. Monodisperse silica nanoparticles were synthesised by the well known Stöber protocol in conjunction with sonication. The nanoparticle size was regulated solely by varying the amount of ammonia solution added. The presence of surface hydroxyl groups was investigated by liquid proton NMR. The resultant nanoparticle size was directly measured by the use of TEM. The synthesised silica nanoparticles were dispersed in acetonitrile (MeCN) and added to a bis acetonitrile gold(I) co-ordination complex [Au(MeCN)2]+ in MeCN. The silica hydroxyl groups were deprotonated in the presence of MeCN generating a formal negative charge on the siloxy groups. This allowed the [Au(MeCN)2]+ complex to undergo ligand exchange with the silica nanoparticles, which formed a surface co-ordination complex with reduction to gold(0), that proceeded by a surface inner sphere electron transfer mechanism. The residual [Au(MeCN)2]+ complex was allowed to react with water, disproportionating into gold(0) and gold(III) respectively, with gold(0) being added to the reduced gold already bound on the silica surface. The so-formed metallic gold seed surface was found to be suitable for the conventional reduction of gold(III) to gold(0) by ascorbic acid. This process generated a thin and uniform gold coating on the silica nanoparticles. This process was modified to include uniformly gold coated composite zinc oxide nanoparticles (Au@ZnO NPs) using surface co-ordination chemistry. AuCl dissolved in acetonitrile (MeCN) supplied chloride ions which were adsorbed onto ZnO NPs. The co-ordinated gold(I) was reduced on the ZnO surface to gold(0) by the inner sphere electron transfer mechanism. Addition of water disproportionated the remaining gold(I) to gold(0) and gold(III). Gold(0) bonded to gold(0) on the NP surface with gold(III) was reduced to gold(0) by ascorbic acid (ASC), which completed the gold coating process. This gold coating process of Au@ZnO NPs was modified to incorporate iodide instead of chloride. ZnO NPs were synthesised by the use of sodium oxide, zinc iodide and potassium iodide in refluxing basic ethanol with iodide controlling the presence of chemisorbed oxygen. These ZnO NPs were treated by the addition of gold(I) chloride dissolved in acetonitrile leaving chloride anions co-ordinated on the ZnO NP surface. This allowed acetonitrile ligands in the added [Au(MeCN)2]+ complex to surface exchange with adsorbed chloride from the dissolved AuCl on the ZnO NP surface. Gold(I) was then reduced by the surface inner sphere electron transfer mechanism. The presence of the reduced gold on the ZnO NPs allowed adsorption of iodide to generate a uniform deposition of gold onto the ZnO NP surface without the use of additional reducing agents or heat.

The chemistry of acid catalyzed delignification of sugarcane bagasse in the ionic liquid trihexyl tetradecyl phosphonium chloride

This article reports on the cleavage of lignin ß-aryl ether bonds in sugarcane bagasse by the ionic liquid (IL) trihexyl tetradecyl phosphonium chloride [P66614] Cl, in the presence of catalytic amounts of mineral acid fca. 0.4%). The deligniflcation process of bagasse was studied over a range of temperatures (120°C to 150°C) by monitoring the production of ß-ketones (indicative of cleavage of ß-aryl ethers) using FTIR spectroscopy and by compositional analysis of the undissolved fractions. Maximum deligniflcation was obtained at 150°C, with 52% of lignin removed from the original lignin content of bagasse. No deligniflcation was observed in the absence of acid, which suggests that the reaction is acid catalyzed with the IL solubilizing the lignin fragments. The rate of deligniflcation was significantly higher at 150°C, suggesting that crossing the glass transition temperature of lignin effects greater freedom of rotation about the propanoid carbon-carbon bonds and leads to increased cleavage of ß-aryl ethers. An attempt has been made to propose a probable mechanism of deligniflcation of bagasse with the phosphonuim IL. © Taylor & Francis Group, LLC.

Mass transfer properties (permeability and mass diffusivity) of four australian hardwood species

Characterization of mass transfer properties was achieved in the longitudinal, radial, and tangential directions for four Australian hardwood species: spotted gum, blackbutt, jarrah, and messmate. Measurement of mass transfer properties for these species was necessary to complement current vacuum drying modeling research. Water-vapour diffusivity was determined in steady state using a specific vapometer. Permeability was determined using a specialized device developed to measure over a wide range of permeability values. Permeability values of some species and material directions were extremely low and undetectable by the mass flow meter device. Hence, a custom system based on volume evolution was conceived to determine very low, previously unpublished, wood permeability values. Mass diffusivity and permeability were lowest for spotted gum and highest for messmate. Except for messmate in the radial direction, the four species measured were less permeable in all directions than the lowest published figures, demonstrating the high impermeability of Australian hardwoods and partly accounting for their relatively slow drying rates. Permeability, water-vapour diffusivity, and associated anisotropic ratio data obtained for messmate were extreme or did not follow typical trends and is consequently the most difficult of the four woods to dry in terms of collapse and checking degradation. © The State of Queensland, Department of Agriculture, Fisheries and Forestry, 2012.

Water absorption, permeability, and resistance to chloride-ion penetration of lightweight aggregate concrete

This paper presents an experimental study to evaluate effect of cumulative lightweight aggregate (LWA) content (including lightweight sand) in concrete [water/cement ratio (w/c) = 0.38] on its water absorption, water permeability, and resistance to chloride-ion penetration. Rapid chloride penetrability test (ASTM C 1202), rapid migration test (NT Build 492), and salt ponding test (AASHTO T 259) were conducted to evaluate the concrete resistance to chloride-ion penetration. The results were compared with those of a cement paste and a control normal weight aggregate concrete (NWAC) with the same w/c and a NWAC (w/c = 0.54) with 28-day compressive strength similar to some of the lightweight aggregate concrete (LWAC). Results indicate that although the total charge passed, migration coefficient, and diffusion coefficient of the LWAC were not significantly different from those of NWAC with the same w/c of 0.38, resistance of the LWAC to chloride penetration decreased with increase in the cumulative LWA content in the concretes. The water penetration depth under pressure and water sorptivity showed, in general, similar trends. The LWAC with only coarse LWA had similar water sorptivity, water permeability coefficient, and resistance to chloride-ion penetration compared to NWAC with similar w/c. The LWAC had lower water sorptivity, water permeability and higher resistance to chloride-ion penetration than the NWAC with similar 28-day strength but higher w/c. Both the NWAC and LWAC had lower sorptivity and higher resistance to chloride-ion penetration than the cement paste with similar w/c.

Development of lightweight concrete with high resistance to water and chloride-ion penetration

This paper presents an experimental study to evaluate the influence of coarse lightweight aggregate (LWA), fine LWA and the quality of the paste matrix on water absorption and permeability, and resistance to chloride-ion penetration in concrete. The results indicate that incorporation of pre-soaked coarse LWA in concrete increases water sorptivity and permeability slightly compared to normal weight concrete (NWC) of similar water-to-cementitious materials ratio (w/cm). Furthermore, resistance of the sand lightweight concrete (LWC) to water permeability and chloride-ion penetration decreases with an increase in porosity of the coarse LWA. The use of fine LWA including a crushed fraction <1.18 mm reduced resistance of the all-LWC to water and chloride-ion penetration compared with the sand-LWC which has the same coarse LWA. Overall, the quality of the paste matrix was dominant in controlling the transport properties of the concrete, regardless of porosity of the aggregates used. With low w/cm and silica fume, low unit weight LWC (_1300 kg/m3) was produced with a higher resistance to water and chloride-ion penetration compared with NWC and LWC of higher unit weights.

Effect of cumulative lightweight aggregate volume in concrete on its resistance to chloride-ion penetration

This paper presents an experimental study on the resistance of lightweight aggregate concretes to chloride-ion penetration in comparison to that of normal weight concrete of similar w/c. Salt ponding test (based on AASHTO T 259), rapid chloride permeability test (ASTM C 1202) and rapid migration test (NT Build 492) were carried out to evaluate the concrete resistance to the chloride-ion penetration. Results indicate that in general the resistance of the LWAC to the chloride-ion penetration was in the same order as that of NWAC of similar w/c. However, the increase in cumulative LWA volume and the incorporation of finer LWA particles led to higher charge passed, migration coefficient, and diffusion coefficient. Since the LWACs had lower 28-day compressive strength compared with that of the NWAC of similar w/c, the LWACs may have equal or better resistance to the chloride-ion penetration compared with the NWAC of equivalent strength. The trend of the resistance of concretes to chloride-ion penetration determined by the three test methods was reasonably consistent although there were some discrepancies due to different test methods.

Estimation Of concrete resistance To chloride-ion penetration based On water accessible porosity and unit weight Of concrete

To ensure better concrete quality and long-term durability, there has been an increasing focus in recent years on the development of test methods for quality control of concrete. This paper presents a study to evaluate the effect of water accessible porosity and oven-dry unit weight on the resistance of concrete to chloride-ion penetration. Based on the experimental results and regression analyses, empirical relationships of the charge passed (ASTM C 1202) and chloride migration coefficient (NT Build 492) versus the water accessible porosity and oven dry unit weight of the concrete are established. Using basic physical properties of water accessible porosity and oven dry unit weight which can be easily determined, total charge passed and migration coefficient of the concrete can be estimated for quality control and for estimating durability of concrete.

Water and chloride ion penetration resistance of highstrength ultra lightweight cement composite

Durability is a significant issue to focus on for newly developed structural lightweight cement composite (ULCC). This paper presents an experimental study to evaluate the resistance of ULCC to water and chloride ion penetration. Chloride penetrability and sorptivity were evaluated for ULCC (unit weight about 1450 kg/m3) and compared with those of a normal weight concrete (NWC), a lightweight aggregate concrete (LWC), and an ultra lightweight composite with proprietary cementitious binder (DB) (unit weight about 1450 kg/m3) at similar compressive strength of about 60 MPa. Rapid chloride penetrability test, rapid migration test, water absorption (sorptivity) test, and water permeability test were conducted on these mixtures. Results indicate that ULCC and DB had comparable performance. Compared with control LWC and NWC at similar strength level, the ULCC and DB mixtures had higher resistance to chloride ion penetration, lower water absorption and virtually impermeable to water penetration.

Development of lightweight aggregate concrete with high resistance to water and chloride-ion penetration

This paper presents an experimental study to evaluate the effect of coarse and fine LWA in concrete on its water absorption and permeability, and resistance to chloride-ion penetration. In additions, LWC with lower unit weight of about 1300 kg/m3 but high resistance to water and chloride-ion penetration was developed and evaluated. The results indicate that the incorporation of coarse LWA in concrete increases water sorptivity and permeability slightly compared to NWC of similar w/c. The resistance of the sand-LWC to chloride-ion penetration depends on porosity of the coarse LWA. Fine LWA has more influence on the transport proper-ties of concrete than coarse LWA. Use of lightweight crushed sand <1.18 mm reduced the resistance of the LWC to water and chloride-ion penetration to some extent. With low w/cm and silica fume, low unit weight LWC (~1300 kg/m3) was produced with higher resistance to water and chloride ion penetration compared with concretes of higher unit weights.

A variable diffusivity model for the drying of spherical food particulates

An investigation of the drying of spherical food particles was performed, using peas as the model material. In the development of a mathematical model for drying curves, moisture diffusion was modelled using Fick’s second law for mass transfer. The resulting partial differential equation was solved using a forward-time central-space finite difference approximation, with the assumption of variable effective diffusivity. In order to test the model, experimental data was collected for the drying of green peas in a fluidised bed at three drying temperatures. Through fitting three equation types for effective diffusivity to the data, it was found that a linear equation form, in which diffusivity increased with decreasing moisture content, was most appropriate. The final model accurately described the drying curves of the three experimental temperatures, with an R2 value greater than 98.6% for all temperatures.

Are in vitro estimates of cell diffusivity and cell proliferation rate sensitive to assay geometry?

Cells respond to various biochemical and physical cues during wound–healing and tumour progression. In vitro assays used to study these processes are typically conducted in one particular geometry and it is unclear how the assay geometry affects the capacity of cell populations to spread, or whether the relevant mechanisms, such as cell motility and cell proliferation, are somehow sensitive to the geometry of the assay. In this work we use a circular barrier assay to characterise the spreading of cell populations in two different geometries. Assay 1 describes a tumour–like geometry where a cell population spreads outwards into an open space. Assay 2 describes a wound–like geometry where a cell population spreads inwards to close a void. We use a combination of discrete and continuum mathematical models and automated image processing methods to obtain independent estimates of the effective cell diffusivity, D, and the effective cell proliferation rate, λ. Using our parameterised mathematical model we confirm that our estimates of D and λ accurately predict the time–evolution of the location of the leading edge and the cell density profiles for both assay 1 and assay 2. Our work suggests that the effective cell diffusivity is up to 50% lower for assay 2 compared to assay 1, whereas the effective cell proliferation rate is up to 30% lower for assay 2 compared to assay 1.

A variable diffusivity model for the drying of spherical food particulates

An investigation of the drying of spherical food particles was performed, using peas as the model material. In the development of a mathematical model for drying curves, moisture diffusion was modelled using Fick’s second law for mass transfer. The resulting partial differential equation was solved using a forward-time central-space finite difference approximation, with the assumption of variable effective diffusivity. In order to test the model, experimental data was collected for the drying of green peas in a fluidised bed at three drying temperatures. Through fitting three equation types for effective diffusivity to the data, it was found that a linear equation form, in which diffusivity increased with decreasing moisture content, was most appropriate. The final model accurately described the drying curves of the three experimental temperatures, with an R2 value greater than 98.6% for all temperatures.