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Densities and viscosities of binary mixtures containing 1-butyl-3-methylimidazolium tetrafluoroborate with water over the salt-rich region concentrations are reported for a temperature range of (283.15 to 373.15) K and compared with literature. The temperature dependence of the mixture densities and dynamic viscosities are accurately described by an empirical, linear relationship and by the Vogel-Fulcher-Tammann (VFT) equation, respectively. We identify a correlation between the excess mixture viscosity and the excess molar volume in the ionic liquid rich regime that is motivated by free volume theory. The broader validity of this correlation is tested against literature data for aqueous mixtures of similar ionic liquids. [ABSTRACT FROM AUTHOR]

Environmental contamination is supposed to be a reason for population declines in reptiles. Especially intensification and expansion of agriculture are leading to increased pesticide exposure risks for wildlife. In the European Union, Special Areas of Conservation (SACs) have been established for the conservation of taxa listed in Annex II of the Habitats Directive. In the SACs, agricultural land use is legal. Therefore, we conducted a risk evaluation of pesticide exposure for Annex II reptiles by calculating proportions of land use with regular pesticide applications within SACs. Using three evaluation factors (occurrence probability, physiology, life-history aspects), a species-specific risk index was created. Nearly half of the species at above-average risk by pesticide use are globally threatened with extinction (IUCN Red List of Threatened Species). About 30% of their SACs are agriculturally used and one priority subspecies of the Habitats Directive is at highest risk ( Vipera ursinii rakosiensis ). Also, all evaluated fresh-water and land-dwelling turtle species are at high risk. National variation in agricultural land use in the SACs was observed. Species at above-average risk are mainly distributed in the Mediterranean and Pannonian/Continental biogeographical regions of Europe. Conservation status according to the IUCN Red List of Threatened Species as well as national differences among the member states argue for the inclusion of pesticide risk assessments in site-specific management plans for SACs to avoid regional loss of reptilian biodiversity. [ABSTRACT FROM AUTHOR]

Cultivation of herbicide-tolerant crops involves repeated applications of the complementary herbicide throughout the growing season, while in conventional corn production, herbicide application is restricted to the beginning of cultivation. Repeated application of herbicides increases both the likelihood an organism will be exposed to the herbicide and the concentration it may be exposed to. We examined effects of short and pulsed exposure of the cycloxydim-based herbicide formulation Focus® Ultra at doses close to the calculated LC5 (0.01 and 0.5 mg a.i. L −1 ) and LC10 values (0.05 and 1.0 mg a.i. L −1 ) on early premetamorphic and prometamorphice larvae of two anuran model organisms, Xenopus laevis and Discoglossus scovazzi . In addition, larvae were repeatedly exposed, i.e. at all considered developmental stages. The herbicide did not induce effects on body size at and time to metamorphosis or increase deformation rates in both species. Exposure to calculated LC5 values did not increase mortality or cause clinical signs in both species. At calculated LC10 values, narcotic effects were seen in all developmental stages. There was no clear evidence of developmental-specific mortality. Metamorphic success was independent of time point and duration of application in X. laevis. Only repeated exposure significantly increased mortality at metamorphosis in D. scovazzi . Narcosis may result in increased mortality under field conditions due to rise of predation risk. Different sensitivity of the test species to the compound was attributed to their physiological properties. Different filtering rates were understood as an accompanying factor influencing exposition. [ABSTRACT FROM AUTHOR]

Measurements of the nanoscale structure of chromatographic adsorbents and the associated distribution of sorbed protein within the media can facilitate improvements in such media. We demonstrate a new technique for this purpose using small-angle neutron scattering (SANS) to characterize the nano- to microscale structure of the chromatographic media and sorbed protein under conditions relevant for preparative chromatographic separations. The adsorption of lysozyme on cellulosic S HyperCel™ (Pall Corporation), a strong cation exchanger, was investigated by SANS. The scattering spectrum is reduced to three contributions arising from (1) the chromatographic medium, (2) discrete protein molecules, and (3) the distribution of sorbed protein within the medium. These contributions are quantified for a range of protein loadings. The total concentration of protein in the chromatographic media can be quantified from the SANS spectrum and the protein is observed to retain its tertiary structure upon adsorption, within the resolution of the method. Further analysis of the SANS spectra shows that protein adsorption is uniform in the media. These measurement techniques provide new and valuable nanoscale information about protein sorption in chromatographic media. [ABSTRACT FROM AUTHOR]

Among the multitude of reasons identified for amphibian decline, increased use of agrochemicals is suggested to contribute to amphibian population changes in industrialized countries. Contamination of breeding ponds with agrochemicals can provoke developmental effects. Deformation rates of tadpoles and metamorphs thus are expected to be high under agrarian land use. Deformation rates >5% is considered unnatural and implemented in a current amphibian monitoring guideline. We examined deformation rates and different endpoints at metamorphosis in Common frog (Rana temporaria) breeding sites (natural wetlands vs. studied waters under potential influence of agrochemicals). Deformation rates were not lower and metamorphosis success was not higher in natural wetlands, but deformation rates >5% were only found here. Rather natural abiotic factors led to higher deformation rates. Our study suggests that the 5%-threshold for unnatural deformation rates should be seen in a critical way until further evaluation if deformation rates of free living amphibians are suitable indicators for environmental pollution. [ABSTRACT FROM AUTHOR]

Environmental contaminants like pesticides concern amphibian conservationists. For many European amphibian species, special areas of conservation were created as they are listed in Annex II of the EU Habitats Directive. Agriculture is not prohibited within these conservation areas. In the present study, a risk evaluation at the European level was conducted to identify proportions of land use with regular pesticide applications within the conservation areas and the specific risk of pesticide exposure depending on the species' biology and ecology. The proportion of agricultural land use and the risk of habitat and individual contamination differ among species but also at national scale. Nearly all species with high risk of habitat pesticide exposure are not threatened within their entire territories and Europe. Conversely, most globally threatened and European priority species are at a lower exposure risk in their habitats - with the exceptionsRana latastei, Pelobates fuscus insubricus, Triturus dobrogicus and Discoglossus jeanneae. In the conservation areas for these species, Habitat Directive management plans need to consider monitoring of habitat contamination with pesticides. Such a monitoring should also be conducted in conservation areas for amphibians that seem to be not threatened yet but are at high exposure risk, e.g. Bombina bombina. Monitoring and conservation action should also take place site-specifically to avoid national or regional loss of amphibian biodiversity. Overall, intensive use of agrochemicals and recent land use changes have the potential to be a serious threat for amphibian species, which can be found within cultivated areas - regardless of their current IUCN status. [ABSTRACT FROM AUTHOR]

Abstract: The complex rheological behaviour of suspensions is very strongly affected by the details of the microstructure and the interparticle forces by which it is controlled. The difficulties involved in characterizing the microstructure, in particular during flow, caused the development of suspension rheology to lag behind that of polymer rheology. Progress in theory, experiments and simulation is rapidly changing the picture, providing opportunities for further significant developments. Possible evolutions in six areas of suspension rheology are discussed here. [Copyright &y& Elsevier]

Abstract: Flow can induce reversible and irreversible structural changes in dispersions. The analysis of flow effects on microstructure and rheology remains one of the challenging problems in colloid science. The rheological manifestation of flow-induced structural changes is a variable viscosity. If the changes are reversible and time dependent, the effect is called thixotropy. The basic elements of this concept are reviewed here, including its definition and the relation with nonlinear viscoelasticity. The omnipresence of thixotropy is illustrated with a wide range of examples from natural and manmade colloidal systems. Its various rheological manifestations are reviewed as well as possible measurement procedures. The microstructural changes due to flow are quite complex and not fully understood. Existing models for thixotropic suspension rheology are categorized and evaluated. [Copyright &y& Elsevier]

Future human space exploration and habitation on the lunar and Martian surfaces necessitates in-situ resource utilization (ISRU) for the development of construction materials tailored for infrastructure and environmental protection. Here we explore the use of lunar and Martian regoliths to create construction materials with properties suitable for such structures as landing pads. Alkali activation of a spectrum of lunar and Martian regolith simulants generates geopolymer binders under ambient and vacuum curing conditions as well as exposure to extreme high and low temperatures (600 and −80 °C). Compressive strength is reduced for binders prepared from each simulant after curing under vacuum and exposure to sub-zero temperatures. In lunar simulant binders, the compressive strength is increased after heating to 600 °C, but the opposite effect is observed in the Martian simulant binder. Amorphous aluminosilicate content and percentage of small particles in the simulants are hypothesized to have a positive impact on compressive strength under ambient curing. Iron and magnesium content may be responsible for decreased compressive strength of the Martian binder after heating. This study offers a robust framework for comparing performance of different simulants under the same curing protocols and environmental exposures, as well as offering insight as to the effects of vacuum curing, and exposure to high and low temperature environments on cured binder samples. Developing a landing pad by transporting activator to the lunar surface is shown to be conceptually feasible within current payload constraints. [ABSTRACT FROM AUTHOR]

In-situ resource utilization (ISRU) to construct environmental protection and critical infrastructure is required for long-term human habitation on the Moon and Mars. Analogous to terrestrial construction materials formed from aluminosilicates, i.e., geopolymers, construction materials formed from lunar aluminosilicate regolith are a promising method to create lunar landing pads and habitats. Building on a previous lateral study across multiple regolith simulants, the effects of composition on one specific regolith simulant, Black Point 1 (BP-1), are investigated with the goal of developing relationships between composition and properties. The effects of overall geopolymer composition, activating solution silica and sodium content, and activating solution water content on seven-day compressive strength, strain to fail, and secant modulus are investigated. Decreasing water content has a positive effect on compressive strength and secant modulus of geopolymers formed at ambient-earth conditions, reaching maximum compressive strength at 75 wt% BP-1. Above a compositional limit of Si/H 2 O = 0.6, differences in Si and Al coordination result in variations in compressive strength with the elemental composition of the geopolymer. At high solids in formulation, the observed trend in compressive strength is nonmonotonic with varying silicon and aluminum content, emphasizing the need for a mechanistic understanding of the relationship between composition and structure for optimization of geopolymer material properties. This study provides a robust set of data for a widely available lunar regolith simulant that can guide further development of processing strategies for lunar ISRU. [ABSTRACT FROM AUTHOR]

• The method to study the microstructure of asphalt binders by SANS was established. • The microstructure of asphalt binders was found and the micelle size was calculated. • The relationship between rheological properties and microstructure of asphalt was analyzed. • The SBS modified mechanism was proved by SANS. The microstructure of asphalt binders is believed to have a significant impact on the performance of binders used in roadway constructions. However, there are only limited studies of their nanoscale to microscale structures. Here, small angle neutron scattering (SANS) is used to study the nanoscale structure of neat asphalt binder, styrene-butadienestyrene (SBS) block copolymers and SBS modified asphalt binder. The SANS pattern for asphalt binder demonstrates that it exhibits a colloidal structure comprised of asphaltenes surrounded by resins dispersed in saturates and aromatics. Fractal-core-shell model fits to these patterns indicate that the asphaltene core size decreases with increasing temperature. Both SANS and rheology confirm that SBS modified asphalt has a thermo-reversible phase transition around 110 °C, where the SBS micelles swell and lose scattering contrast above this temperature. The thermo-reversibility of this phenomenon indicates that the mechanism of SBS modification is mostly a physical modification of the nanoscale structure as proposed in the colloidal model of asphalt. Modeling of the SANS patterns shows that neat SBS and SBS dispersed in asphalt binder have a lamellar structure surrounded by a shell. These results are useful for understanding the relationship between the nanoscale structure of asphalt binder and pavement performance, as well as potentially developing new types of modified asphalt binders. [ABSTRACT FROM AUTHOR]

A unique feature of inorganic membranes is the ability to operate at high temperature and pressure. Even supercritical solvents can be processed by these membranes, whereas polymer membranes tend to swell and consequently suffer from reduced selectivity and mechanical strength. Carbon membranes open new possibilities, e.g. the processing of high pressure, high temperature fluid streams directly in place or the use in membrane reactors for chemical reactions like H 2 -synthesis by dehydrogenation. This work investigates high pressure adsorption of carbon membrane material for different gases at up to 12 MPa, the selectivity and permeance for CO 2 /N 2 mixtures in a pressure range from 0.1 to 20 MPa and the swelling of carbon material exposed to Oxygen at up to 10 MPa. A model based on Maxwell-Stefan diffusion with parameters gained from measured adsorption and fluxes has been implemented to improve the understanding of the behaviour of high pressure separation with carbon membranes. [ABSTRACT FROM AUTHOR]

Environmental pollution and habitat loss are described as underlying causes for population declines in reptiles and especially affect species in agricultural landscapes. Studies dealing with effects of pesticide exposure on reptiles are limited, mainly addressing the orders Testudines and Crocodylia, but largely neglecting the most diverse reptile order Squamata (lizards and snakes). As a consequence, information regarding effects on their organisms, as well as exposure probability and pesticide uptake in the Reptilia has to be considered rather uncharted. We here ask how pesticide applications affect a widely distributed, synanthropic squamate species in Europe. We studied the common wall lizard ( Podarcis muralis ) with regard to enzymatic biomarkers of pesticide exposure (Glutathione-S-Transferase, Glutathione Reductase, Acetylcholinesterase) and body condition. Lizards were sampled from wild populations, along an exposure gradient (three exposed sites with differing land use intensity and one reference site). Our results suggest both dermal and oral uptake of pesticide formulations, with the former being especially relevant during the first two days after a pesticide application. Enzymatic activity slightly differed between exposure gradients, while showing overall similar patterns. Body condition of lizards decreased with increasing pesticide exposure. Furthermore, gender distribution was particularly skewed in favor to males within exposed sample sites. Although reptiles are not target organisms of pesticide applications, many species do come into contact with them, and most probably suffer from dermal and oral uptake. Thus, we believe it is indispensable for reptiles to be integrated in risk assessments in order to improve conservation practice. [ABSTRACT FROM AUTHOR]

Multi-injection pharmaceutical products such as insulin must be formulated to prevent aggregation and microbial contamination. Small-molecule preservatives and nonionic surfactants such as poloxamer 188 (P188) are thus often employed in protein drug formulations. However, mixtures of preservatives and surfactants can induce aggregation and even phase separation over time, despite the fact that all components are well dissolvable when used alone in aqueous solution. A systematic study is conducted here to understand the phase behavior and morphological causes of aggregation of P188 in the presence of the preservatives phenol and benzyl alcohol, primarily using small-angle x-ray scattering (SAXS). Based on SAXS results, P188 remains as unimers in solution when below a certain phenol concentration. Upon increasing the phenol concentration, a regime of micelle formation is observed due to the interaction between P188 and phenol. Further increasing the phenol concentration causes mixtures to become turbid and phase-separate over time. The effect of benzyl alcohol on the phase behavior is also investigated. [ABSTRACT FROM AUTHOR]

• New apparatus: a large coaxial cell with a flow through system for high frequency broadband dielectric spectroscopy. • Calibration based on a single measurement made on reference liquid (deionized water) • Computation of complex permittivity performed based on iterative solver or optimization method using a frequency dependent model of the complex permittivity. • High performance obtained for the determination of the real part of the complex permittivity and good performance for the determination of the imaginary part of the complex permittivity. This paper presents a new apparatus: a large flow through coaxial cell designed for broadband dielectric characterization of material under controlled hydraulic and chemical boundaries. The cell is calibrated with a single measurement made on a perfectly known dielectric liquid (deionized water) together with an optimization procedure. Then, two methods are proposed to compute the dielectric characteristics: an iterative solver and an optimization method. These two methods are systematically investigated for two reference liquids: a low loss dielectric material (ethylene glycol) and high loss dielectric liquid (saline solutions with different concentration). Tabulated data were used to perform a quantitative error analysis in terms of estimated complex permittivity. The results have shown high performance in terms of real part and good performance in terms of real part. The measurements on saline solution also highlight the impact of electrode polarization with dramatic effect in the lower part of the frequency range. [ABSTRACT FROM AUTHOR]

The topology of self-assembled surfactant solutions includes varying degrees of micellar branching, ranging from linear wormlike micelles to a micellar network. Micellar branching acts as an effective attraction between micelles such that network condensation can lead to phase separation. Unlike chemical branching in polymers, micellar branches are labile. Movement of branches along a micelle contour has therefore been proposed as a mechanism of stress relaxation that leads to a reduction in the structural relaxation time and thus, the zero-shear viscosity. Branching is also thought to suppress flow alignment, and for lower levels of branching, may also suppress instabilities such as shear banding. The suppression of shear banding can lead to a lesser degree of shear-thinning in the apparent viscosity at higher shear rates, as well as a reduction in extensional thickening. However, for higher levels of branching, shear can induce branching for samples in proximity to such a phase transition, which can result in shear banding due to shear-induced phase separation. Recent modeling and simulations of the energetics of branching, as well as experiments on model systems, show that the reduction in zero-shear viscosity is due to micelle branching. Current research includes efforts to develop a more mechanistic, quantitative understanding of micellar branching and more generally, its effects on micellar solution rheology. [ABSTRACT FROM AUTHOR]

• Electrical properties of two saturated clays were investigated in the temperature range 25 °C down to 0 °C. • Impedance analyser measurements (mHz to kHz range) were combined with Vector Network Analyzer measurements (MHz to GHz range). • Temperature effect on typical geophysical quantities was modelled with a mixture approach. Impedance and vector network analyzer measurements are combined in order to measure frequency dependent conductivity and permittivity of two different saturated clays: montmorillonite and illite chlorite. In the low frequency range, the complex conductivity is determined over the 10 mHz to 45 kHz frequency range using a complex impedance analyzer with a 4-electrodes cell. In the high frequency range (50 MHz to 5 GHz), the complex permittivity is obtained from measured reflection factor of an open-ended probe. The ultrabroadband constitutive properties of the saturated clays were investigated in the temperature range 25 °C down to 0 °C. A mixture equation, based on a volume average approach, was applied to model the low and high frequency electrical properties based on the formation factor. The temperature dependency was considered in the following petrophysical quantities: low frequency conductivity, chargeability and high frequency permittivity. The modeled results are in reasonable agreement with measurements. [ABSTRACT FROM AUTHOR]

An extensive data set has been developed and used to further the progress of a model-informed design of controlled drug release. An improved drug-release model with mechanistic modeling of hydrolytic polymer degradation is used and validated by comparing model predictions to in vitro experiments. Combining parameter estimates from the literature with model fits to the data set, this study can aid in achieving a priori design of controlled drug release from a model PLGA release system. A systematic series of model release systems were formulated with FITC-labeled dextran, as a surrogate for biopharmaceuticals, in PLGA rods over a broad range of compositions. While general comparisons between the model and experiments were favorable, important discrepancies were identified for several formulations with significant first-phase drug release. Supported by cross-sectional fluorescence microscopy images of the FITC-dextran distribution within the rods, this first-phase release was attributed to a combination of two main factors: (1) percolation of the drug particles and (2) swelling of and pore formation in the rods due to water uptake. These observations indicate the importance of careful selection of the PLGA polymer grade when designing drug release systems but also reflect a need for better understanding of phenomena such as pore formation. Adapting model parameters, without modifying the physical processes included in the model, enabled accurate fitting of the experimental data for all formulations, highlighting the applicability of the model. [ABSTRACT FROM AUTHOR]

Abstract: Complex fluids with high concentrations of crystallizing fatty acids are important for consumer skin care products. These fluids exhibit solid-like elastic behavior at rest, but yield and flow under an applied strain. Such behavior is characteristic of isotropic, space-filling networks. The processing determines the microstructure of these systems, which in turn influences their macroscopic rheological properties. The kinetics of crystal growth in model system compositions, comprising (by weight) 9% sodium dodecyl sulfate, 3% cocamidopropyl betaine, and different specified amounts of palmitic acid in H2O or D2O, were studied by time domain nuclear magnetic resonance (TDNMR) and differential scanning calorimetry (DSC). The data were analyzed using the Avrami equation; both DSC and TDNMR gave consistent Avrami exponent values of approximately 1.5 for formulations with 11wt% and greater amounts palmitic acid content. The Avrami exponent is consistent with two-dimensional crystal growth limited both by diffusion and surface incorporation. The solids content at 25°C was found to be proportional to the concentration of palmitic acid level above its solubility limit of ca. 2wt%. TDNMR, combined with DSC, microscopy, and rheology provide valuable insights into the molecular structure and mechanism of crystallization in surfactant/fatty acid systems. [Copyright &y& Elsevier]

Abstract: Complex fluids with high concentrations of crystallizing fatty acids are important for consumer care products. The key features of these materials are their ability to support their weight under gravity and to yield or flow beyond a critical applied strain. To better understand the post-processing behavior of these systems, we have utilized a combination of Rheology, Differential Scanning Calorimetry, X-ray scattering, and Polarized Light Microscopy to study a model formulation consisting of two synthetic surfactants and a fatty acid (n-hexadecanoic acid) in water. Homogeneous samples with high storage modulus (G′) are realized due to the formation of a space filling solid fatty acid crystal network. A minimum of 5–7wt% of fatty acid is required to achieve the formation of a percolating crystal network. The storage modulus, yield stress and strain of these formulations show a non-monotonic increase with fatty acid content. This is attributed to the change in the fatty acid crystal habit from large to small aspect ratio plates. We hypothesize that the fatty acid crystal network consists of crystal aggregates linked by surfactant-fatty acid gels, rendering the desired paste-like characteristics to the formulation. The combination of methods utilized in this research provides a framework for understanding crystallizing systems. [Copyright &y& Elsevier]

Abstract: The split Hopkinson pressure bar experimental technique is used to evaluate the squeezing flow response of a concentrated, discontinuously thickening colloidal suspension of spherical silica particles loaded at high stresses/strain rates. These results provide insight into the transitional behavior of these materials, as well as the post-transitional response under compressive loading. A method of analyzing the strain and strain rate dependent behavior is presented to identify modes of material response (viscous, elastic, etc.). Experimental results are presented as stress–strain–strain rate plots and a surface fitting approach is used to develop a phenomenological model describing the overall response. From this model, it is possible to identify regions of elastic and viscous behavior using a gradient analysis approach. It was found that, after an initial period of viscous deformation, the suspension behaves like a viscoelastic material – this regime corresponds well with transition in which large clusters of particles percolate. This is followed by a third, viscous regime in which the material undergoes viscous deformation. At the highest stresses, a plateau region of plastic deformation has been identified. This approach and the conditions under which it may be applied are described in detail in the paper. [Copyright &y& Elsevier]

Abstract: Hydrogel materials are promising vehicles for the delivery of protein therapeutics. Proteins can impart physical interactions, both steric and electrostatic in nature, that influence their release from a given gel network. Here, model proteins of varying hydrodynamic diameter and charge are directly encapsulated and their release studied from electropositive fibrillar hydrogels prepared from the self-assembling peptide, MAX8. Hydrogelation of MAX8 can be triggered in the presence of proteins for their direct encapsulation with neither effect on protein structure nor the hydrogel’s mechanical properties. Bulk release of the encapsulated proteins from the hydrogels was assessed for a month time period at 37 °C before and after syringe delivery of the loaded gels to determine the influence of the protein structure on release. Release of positively charged and neutral proteins was largely governed by the sterics imposed by the network. Conversely, negatively charged proteins interacted strongly with the positively charged fibrillar network, greatly restricting their release to <10% of the initial protein load. Partition and retention studies indicated that electrostatic interactions dictate the amount of protein available for release. Importantly, when protein encapsulated gels were delivered via syringe, the release profiles of the macromolecules show the similar trends as those observed for non-sheared gels. This study demonstrates that proteins can be directly encapsulated in self assembled MAX8 hydrogels, which can then be syringe delivered to a site where subsequent release is controlled by protein structure. [Copyright &y& Elsevier]

Abstract: The behavior of a concentrated, hard-sphere colloidal suspension is evaluated using the split Hopkinson pressure bar (SHPB) experimental technique. The composition of the suspension is measured using thermograviometric analysis before and after loading. This, combined with recorded pressure distributions, result in the conclusion that the suspension undergoes high rate squeezing flow. Experimental results demonstrate that the suspension exhibits shear thickening consistent with that observed in standard rotational rheometry. At sufficiently high stresses the suspension exhibits a second regime of shear thinning behavior that is consistent with elastohydrodynamic theory that incorporates the shear modulus of the particles themselves. Further increases in stress result in irreversible behavior, i.e., rather than fracturing or crushing, the particles form non-reversible agglomerates during testing. This fact is demonstrated through the use of dynamic light scattering and electron microscopy. This behavior occurs within a regime of viscous material response which is seen to occur at normal strain rates and stresses over 104 s−1 and 40MPa, respectively. [Copyright &y& Elsevier]

Abstract: Self-assembling peptide hydrogels are used to directly encapsulate and controllably release model FITC–dextran macromolecules of varying size and hydrodynamic diameters. MAX1 and MAX8 are two peptide sequences with different charge states that have been designed to intramolecularly fold and self assemble into hydrogels at physiological buffer conditions (pH 7.4, 150mm NaCl). When self-assembly is initiated in the presence of dextran or protein probes, these macromolecules are directly encapsulated in the gel. Self-diffusion studies using fluorescence recovery after photobleaching (FRAP) and bulk release studies indicate that macromolecule mobility within, and release out of, these gels can be modulated by varying the hydrogel mesh size. The average mesh size can be modulated by simply varying the concentration of a given peptide used to construct the gel or by altering the peptide sequence. In addition, results suggest that electrostatic interactions between the macromolecules and the peptide network influence mobility and release. Depending on probe size, release half-lives can be varied from 8h to over a month. [Copyright &y& Elsevier]

Structure-property relationships of alkali-activated aluminosilicate gels are studied using rheology, neutron scattering, solid-state NMR, and TEM to develop a pseudo-ternary state diagram. Empirical gel states are classified by the rheological behavior (sol-gel transition and scaling of storage modulus with aluminum concentration). The state boundaries are compared to alkali-activated materials from the literature including denser binders. This work focuses on two compositions of dilute gels, formulated to specifically quantify the effects of pH and aluminum concentration on gel microstructure and rheology. Gels formulated at constant pH of 12.5 show a change in morphology and silicon coordination, but consistent mass fractal dimension as aluminum concentration is increased. This microstructural behavior contrasts the characterization of gels previously formulated with a variable pH (range 3–11) which is dependent on aluminum concentration. These results inform the complicated interactions in the polycondensation reaction of alkali-activated binders and lead to a state diagram which unifies many structure-property observations reported for these materials. Structure-property relationships for two formulations of N-A-S-H gels are compared and plotted in a pseudo-ternary state diagram which includes other compositions of N-A-S-H gels and alkali-activated binders from the literature, shaded according to the scaling of the storage modulus where applicable. [Display omitted] [ABSTRACT FROM AUTHOR]

A new integrated experimental and theoretical framework to simultaneously measure mechanical, hydraulic and high frequency dielectric properties of soil during shrinkage was designed aiming at the development, verification and validation of constitutive electromagnetic material relationships. The electromagnetic response of a soil to a high frequency (radio to microwave) signal contains information that can be harvested to characterise soil including its state variables such as water content, density and soil suction. The developed framework allows decoding of this response. In the presented study on kaolin (i) shrinkage tests ii) shrinkage tests with non-destructive determination of dielectric spectra from 50 MHz to 3 GHz, and (iii) determination of the soil suction relationship over a broad range of water content, have been performed. The results of this investigation show a nonlinear evolution of the permittivity at 1 GHz as a function of water content with a sharp transition. None of the advanced mixture approaches that were applied in a forward approach could quantitatively characterize this relationship between the permittivity and the volumetric water content. With a recently developed advanced mixture equation (Augmented Broadband Complex dielectric Mixture model – ABCM) applied in an inverse scheme, the saturated part of the shrinkage curve was able to be estimated from the permittivity measurements. A quantitative relationship between the cementation exponent within this mixture equation and the soil suction have also been established. The conditions and reasons for the drop in permittivity remains subject of future research. • Linking soil shrinkage – soil water retention – high frequency electromagnetic (HF-EM) properties of soils. • 3 dimensional finite element modelling for vertical sensitivity of the open ended probe. • Forward and inverse approaches to link HF-EM and hydro-mechanical behaviour of kaolin during shrinkage. • Estimation of saturated part of the soil shrinkage curve using Augmented Broadband Complex dielectric Mixture model. • Linear relationship between cementation exponent and soil suction. [ABSTRACT FROM AUTHOR]

Abstract: A microfluidic process for producing crystals of controlled size by confining the crystallization within drops is demonstrated. The process consists of a drop producing stage which segments the mother liquor into monodisperse drops followed by crystallization in a temperature controlled tubular crystallizer. The process is implemented to produce lactose crystals with significantly narrower crystal size distribution (CSD) as compared with crystals produced in a stirred bulk crystallizer. By controlling the drop size and initial supersaturation the mean crystal size can be controlled. The distribution of the number of crystals per drop and the CSD are measured as a function of supersaturation at temperatures between 20 and for 150 and drops. In the case where drops contain only one crystal, a very narrow CSD is obtained with a coefficient of variation of crystal size as low as 7%. The crystallization of lactose in a microfluidic tubular crystallizer is modeled by treating nucleation in drops as a Poisson process with a nucleation rate based on classical nucleation theory. Experimental results are in good agreement with predictions from a Poisson process model over the range of temperatures, supersaturations and drop sizes tested. [Copyright &y& Elsevier]

Abstract: An algorithm has been developed to create structural models for amorphous carbons using Monte Carlo simulations in the canonical ensemble. The simulation method used follows the experimental preparation of nanoporous carbons (NPC) by pyrolysis from polyfurfuryl alcohol as a guideline. The resulting structure exhibits properties that compare favorably to those observed experimentally for real NPCs. These atomistic NPC models are approaching a realistic representation of NPCs used for gas separations and as such, are being used to study the diffusion of small gas molecules in these materials. Limitations of the method and possible improvements are discussed. [Copyright &y& Elsevier]

Small angle neutron scattering (SANS) studies of a model pharmaceutical formulation reveal how formulation stability depends on the compatibility of individual components. Solutions of two common protein formulation excipients, polysorbate 80 (PS80), a nonionic surfactant that prevents aggregation, and m-cresol, an antimicrobial agent for multi-dose injectable formulations, are investigated. The addition of m-cresol to PS80 solutions leads to solution turbidity and irreversibly alters PS80 micelle morphology. This slow preservative-induced destabilization of PS80 micelles progresses over days or even weeks, which highlights the essential role that aggregation kinetics plays in preservative-surfactant interactions. The temperature-dependence of PS80 micelle growth kinetics is quantified by SANS in the presence of m-cresol. Aggregation is a two-step process, where initial formation of small aggregates is followed by a period of monotonic power-law growth, providing evidence for the mechanism. Total aggregate mass stays constant after initial aggregate formation, and addition of a pH-regulating citrate buffer dramatically accelerates aggregation kinetics. [ABSTRACT FROM AUTHOR]

• Application of a multiscale, population balance‐based thixotropy model to blood. • More physical description of the coin‐stack like rouleaux aggregate structures. • Meaningful microscopic structural information obtained by fitting bulk rheology. Modeling blood rheology remains challenging in part because of its multiphase, aggregating colloidal nature that gives rise to complex viscoplastic and time-dependent (thixotropic) behavior. Here, we demonstrate that a multiscale approach incorporating a direct coupling of coarse-graining particle-level modeling to the macroscopic phenomenological modeling can provide new insights and a promising methodology. Specifically, a general population balance-based, multiscale, thixotropic modeling approach, first proposed by Mwasame et al., AIChE J. 63 (2017) 517–531, is applied to account for the rouleaux-induced thixotropy in human blood in shear flow. Population balances offer a compelling alternative to previously proposed structure-based heuristic kinetics models of aggregating colloidal suspensions as they use a statistical approach to describe the aggregate size distribution with well-defined processes for either shear-induced or Brownian aggregation and breakup under shear flow. When applied to human blood, the population balance approach offers a first attempt to model the size evolution of predominantly coin-stack like rouleaux structures of the red blood cells that are the primary source behind the observed yield stress and thixotropy of blood at low shear rates. This microscopic information, suitably coarse-grained, is then introduced into a semi-phenomenological macroscopic model that expresses the total stress in terms of an elastic and viscous contribution. Shear thinning introduced due to the red blood cell deformation at high shear rates is accounted for by following Horner et al., J. Rheol. 62 (2018) 577–591. An advantage of this modeling approach is that the parameters have specific physical meaning that allows for independent estimates and/or evaluations through appropriately designed independent experiments. Conversely, parameters with specific microscopic interpretations, such as the fractal dimension of the aggregates, d f , are obtained fits of macroscopic shear experiments. Fitting and predictions use steady shear, and unidirectional large amplitude oscillatory shear (UD-LAOS) experiments on whole blood samples of two healthy donors, as reported in Horner et al. We obtain values for d f in the range of 1.5 ± 0.2 which is consistent with the rod-like shape of rouleaux structures reported in the literature. Furthermore, the shear predictions compare favorably against the experiments. While this approach is not as accurate as the fits of prior structure kinetics modeling of Horner et al., these promising results provide a pathway for model improvement by including independently verified physical properties of blood. This work demonstrates a new particle-level approach for describing and predicting the non-Newtonian, thixotropic rheology of human blood. [ABSTRACT FROM AUTHOR]

Surfactants are commonly used in therapeutic protein formulations in biopharmaceuticals to impart protein stability; however, their solution morphology and the role of the individual components in these structurally heterogeneous commercial grade surfactants at physiologically and pharmaceutically relevant temperatures have not been investigated systematically. The micellar morphologies of Polysorbate 20 and Polysorbate 80 and their primary components monoester fractions, as well as the diester fractions, are evaluated at 4, 22°C, 40°C, and 50°C using small-angle neutron scattering to determine the aggregation number, radius of gyration, core radius, critical micelle concentration, shell thickness, and shell hydration. The sizes and aggregation numbers of the diester fractions of PS20 above 80°C and PS80 above 50°C exhibit significant changes in shape. The analysis of the small-angle neutron scattering data of PS20 confirms that the critical micellar concentration of the monoester fraction is significantly higher at 4°C compared to the diester fraction and their original material, all-laurate PS20. Overall, these experiments identify the dominant components responsible for the temperature-dependent behavior of these surfactants in pharmaceutical protein formulations. [ABSTRACT FROM AUTHOR]

Mathematical modeling of drug release can aid in the design and development of sustained delivery systems, but the parameter estimation of such models is challenging owing to the nonlinear mathematical structure and complexity and interdependency of the physical processes considered. Highly parameterized models often lead to overfitting, strong parameter correlations, and as a consequence, inaccurate model predictions for systems not explicitly part of the fitting database. Here, we show that an efficient stochastic optimization algorithm can be used not only to find robust estimates of global minima to such complex problems but also to generate metadata that allow quantitative evaluation of parameter sensitivity and correlation, which can be used for further model refinement and development. A practical methodology is described through the analysis of a predictive drug release model on published experimental data sets. The model is then used to design a zeroth-order release profile in an experimental system consisting of an antibody fragment in a poly(lactic-co-glycolic acid) solvent depot, which is validated experimentally. This approach allows rational decision-making when developing new models, selecting models for a specific application, or designing formulations for experimental trials. [ABSTRACT FROM AUTHOR]

The use of enzymatic biomarkers constitutes a widely used approach in ecotoxicology. However, standard sampling procedures are invasive, requiring tissue, organ or blood extraction. This leads to concerns regarding conservation practice, animal welfare and restrictions in study design. New techniques are needed to avoid these problems, but still generate reliable data. Here, we aimed at validating the use of buccal swabs as a reliable method to detect pesticide exposure in reptiles. Common wall lizards (Podarcis muralis) were divided into control, dermal and oral treatment groups and exposed to different pesticide formulations. Subsequently, buccal swabs were taken and enzymatic activity was analyzed. We were able to confirm the suitability of the method to detect effects of pesticide exposure on the enzymatic level. While exposure to the formulation Roundup Ultramax® didn't match when compared to effects previously observed in situ when compared to other glyphosate based formulations, effects could still be detected. This can be seen as a strong indicator that the active ingredient of a formulation may not always be the mian driver for ecotoxicological effectsat the enzymatic level. At the same time, exposure towards the single formulation Vivando® didn't result in any effects. However, individuals residing in agricultural landscapes will mostly be exposed to pesticide mixes containing different formulations. Our results strongly advocate that buccal swabbing is a reliable minimal invasive method to generate samples for detecting effects of pesticide exposure in reptiles. Due to its easy handling, we believe it will provide new opportunities concerning study designs. • Buccal swabs are a reliable method to detect effects of pesticide exposure. • Dermal and oral exposure pathways can be detected separately. • The Method works well for pesticide mixes and herbicides. • No effects could be detected with very small amounts of pesticide. • Neurotoxic effects could not be observed. [ABSTRACT FROM AUTHOR]

Understanding the adsorption of protein and surfactant molecules on hydrophobic surfaces is very important for storage stability and delivery of pharmaceutical liquid formulations as many commonly-used devices, such as drug containers and syringes, have hydrophobic surfaces. Neutron reflectometry is used here to investigate the structure information of the adsorption process of non-ionic surfactant (polysorbate 20) and proteins (monoclonal antibody (mAb) and lysozyme) on polystyrene surfaces. Thickness of adsorbed polysorbate 20 thin film is observed to be ≈21 Å, comparable to the radius of gyration of polysorbate 20 micelles in solution. Although no lysozyme adsorption is observed on the polystyrene surface in low solution pH condition, the mAb can be strongly absorbed on the polystyrene surface with a layer thickness of ≈145 Å. The mAb concentration near the surface is about 135 mg/ml significantly larger than the bulk protein concentration. The differences in adsorption behavior are attributed to different protein interactions with a hydrophobic surface. Further, both surfactants and proteins adsorbed on the polystyrene surfaces can not be rinsed off using pure water. [ABSTRACT FROM AUTHOR]

The low-earth orbit environment contains small micrometeoroid and orbital debris (MMOD) particles traveling at characteristic velocities of several kilometers per second. In addition to being a direct threat to astronauts and spacecraft, upon impact with the exterior surface of a space vehicle, these highly energetic MMOD particles can create cut and puncture hazards for astronauts performing extra-vehicular activities (EVA). In this work, we demonstrate that replacing the standard neoprene-coated nylon absorber layers with woven aramid textiles intercalated with colloidal shear thickening fluids, i.e., STF-Armor™, can provide a meaningful enhancement to the cut and puncture resistance of the thermal micrometeoroid garment (TMG). Quasi-static puncture testing is performed using hypodermic needles of varying gauge to simulate the cutting and puncture hazards at deformation rates characteristic of human motion. At equal areal densities, we find that a TMG lay-up containing STF-Armor™ greatly improves puncture protection with a reduction in weight and comparable flexibility. [ABSTRACT FROM AUTHOR]

We study the rheology of dense suspensions of non-Brownian repulsive particles. The suspensions consist of two-dimensional discoidal particles confined by walls orthogonal to the shear gradient direction and are simulated by the method of smoothed particle hydrodynamics. The strength of hydrodynamic shear thickening is primarily determined by the distribution of hydrodynamic clusters formed during shear flow while confinement plays a geometrical role and indirectly affects viscosity. Under strong confinement a percolating network of clusters develops into a jamming structure at high shear rate and as a result, the viscosity increases substantially. Extrapolating the viscosity to the limit of very weak confinement shows that confinement is essential to observe hydrodynamic shear thickening in these non-Brownian suspensions. [ABSTRACT FROM AUTHOR]

Abstract: Targeted delivery of imaging agents to cells can be optimized with the understanding of uptake and efflux rates. Cellular uptake of macromolecules is studied frequently with fluorescent probes. We hypothesized that the internalization and efflux of fluorescently labeled macromolecules into and out of mammalian cells could be quantified by confocal microscopy to determine the rate of uptake and efflux, from which the mass transfer coefficient is calculated. The cellular influx and efflux of a third generation poly(amido amine) (PAMAM) dendrimer labeled with an Alexa Fluor 555 dye was measured in Capan-1 pancreatic cancer cells using confocal fluorescence microscopy. The Capan-1 cells were also labeled with 5-chloromethylfluorescein diacetate (CMFDA) green cell tracker dye to delineate cellular boundaries. A dilution curve of the fluorescently labeled PAMAM dendrimer enabled quantification of the concentration of dendrimer in the cell. A simple mass transfer model described the uptake and efflux behavior of the PAMAM dendrimer. The effective mass transfer coefficient was found to be 0.054±0.043μm/min, which corresponds to a rate constant of 0.035±0.023min−1 for uptake of the PAMAM dendrimer into the Capan-1 cells. The effective mass transfer coefficient was shown to predict the efflux behavior of the PAMAM dendrimer from the cell if the fraction of labeled dendrimer undergoing non-specific binding is accounted for. This work introduces a novel method to quantify the mass transfer behavior of fluorescently labeled macromolecules into mammalian cells. [Copyright &y& Elsevier]

Abstract: We present a simplified approach to understanding the mechanics of stable electrospinning jets based on electrohydrodynamic theory that explicitly incorporates the extensional rheology of polymeric fluids. Flow regimes of electrospun jets are identified by analogy to uniaxial extension of a fluid jet. These flow regimes predict the limiting kinematics of electrospinning jets and identify dimensionless parameters important to the control and operation of electrospinning processes. In situ kinematic measurements validate model assumptions and scaling predictions, and allow the reduction of entire jet radius and velocity profiles to several key parameters. The model predictions are shown to hold both above and below the entanglement concentration, as well as for solutions with added electrolyte and increased conductivity. The analysis also enables direct measurement of the apparent extensional viscosity of solutions at the high extension rates experienced during electrospinning. Finally, dimensional analysis of the model yields a correlation for electrospun fiber diameter in terms of measurable fluid properties, controlled process parameters, and measured jet variables, demonstrating the influence of mechanics in the straight portion of the jet on ultimate fiber morphology. [Copyright &y& Elsevier]

• Design of a new probe to study the spatial distribution of frequency dependent electromagnetic properties. • Validation of the performance of the probe against reference liquids. • Application to study the spatial distribution of soil properties during dewatering. This paper reports the design, the calibration and the application of a multiple open-ended coaxial probe. The objective behind development of this new sensor is to characterize the spatial and temporal distribution of electromagnetic properties of materials in frequency domain (radio to microwave region). Complex permittivity has been computed from the measured scattering function based on a capacitance model. Each of the probes have been calibrated against measurements performed on reference materials air, deionized water and methanol, for which dielectric properties are well established. The quality of the calibration has been validated with measurement made on another reference liquid (ethylene glycol) by comparing with results from the literature. The new sensor has then been used to measure the temporal and spatial electromagnetic properties over the 50 MHz–3 GHz frequency range of a reference geomaterial (kaolin) during evaporative dewatering. For this material, spatial porosities and gravimetric moisture contents have been estimated based on an advanced mixture model from the measured complex permittivity. Finally, the results have been compared with the average moisture content values obtained from gravimetric measurements. This paper, therefore, underpins the development of robust monitoring systems based on EM methods to study the spatial distribution of state parameters during evaporative dewatering processes. [ABSTRACT FROM AUTHOR]