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We investigate the aging behavior in a well-studied model system comprised of a colloidal suspension of thermoreversible adhesive hard spheres (AHS) but thermally quenched below the gel transition to much larger depths than previously studied. The aging behavior in the model AHS system is monitored by small amplitude oscillatory shear rheology measurements conducted while rapidly quenching from the liquid state at 40 °C to a temperature below the gel temperature, and new, anomalous aging behaviors are observed. Shallow quenches lead to monotonic development of the elastic modulus with time, consistent with prior reports for the development of a homogeneous gel [Gordon et al., J. Rheol. 61, 23–34 (2017)]. However, for deeper quenches, a unique and new phenomenon is reported, namely, after an initial rise in the modulus, a reproducible drop in the modulus is observed, followed by a plateau in the modulus value. This drop can be gradual or sudden and the extent of the drop depends on the quench depth. After this drop in the modulus, AHS gel evolves toward a quench-path independent state over the experimental timescale. These effects of the extent of quenching on aging behavior are hypothesized to be a consequence of quenching into different underlying thermodynamic states of colloidal gels and the possible influence of the adhesive glass dynamical arrest for the deepest quenches. The research connects homogeneous gelation with heterogeneous gel formation due to phase separation and shows that the extent of quench can be used as an independent parameter to govern the rheological response of the arrested gel. [ABSTRACT FROM AUTHOR]

Starting from a suspension of elastic dumbbells or chain-like particle aggregates as a simple model of a viscoelastic liquid, the rheological equation of state is inductively derived into which the concept of an "elastic strain component" (recoverable strain) is incorporated and can be understood as a nonlinear extension of the so-called "generalized Maxwell model." Here, the liquid is characterized by a sequence of nested continua, each associated with an elasticity law. The consideration of the directional dependence of the mobility of the structural elements requires that the behavior of the liquids represented in this way generally deviates from a Weissenberg liquid. [ABSTRACT FROM AUTHOR]

Alkali-activated aluminosilicate (N-A-S–H) gels are models for understanding structure formation in sustainable cement alternatives known as geopolymers. Temporal measurements of elastic shear moduli development of these aluminosilicate gels show systematic trends in kinetics with respect to silicon to aluminum (Si/Al) ratio. This behavior can be reduced to a single master curve when nondimensionalized with the Si/Al-dependent gel time and equilibrium modulus. An autocatalytic reaction model and Avrami model fit the master curve well. The Avrami exponent is 1.5, consistent with the nucleation and growth steps separately modeled in the autocatalytic reaction model, and further is within the expected values for diffusion-limited growth suggested from independent measurements of the structural fractal dimension by neutron scattering. These results unifying rheokinetic behavior over a range of gel compositions suggest a common underlying microstructure development in such gels and the possibility of developing predictive models for property development in geopolymers more broadly. An autocatalytic reaction kinetic model describing nucleation and growth is fit to the evolution of the storage modulus, G', of alkali-activated aluminosilicate gels with varying concentration of aluminum ( S i / A l / N a = 2 / n Al / 1.5 ). A master curve is constructed by nondimensionalizing the timescale and storage modulus of each dataset. [ABSTRACT FROM AUTHOR]

In this work, we outline the development of a thermodynamically consistent microscopic model for a suspension of aggregating particles under arbitrary, inertia-less deformation. As a proof-of-concept, we show how the combination of a simplified population-balance-based description of the aggregating particle microstructure along with the use of the single-generator bracket description of nonequilibrium thermodynamics, which leads naturally to the formulation of the model equations. Notable elements of the model are a lognormal distribution for the aggregate size population, a population balance-based model of the aggregation and breakup processes and a conformation tensor-based viscoelastic description of the elastic network of the particle aggregates. The resulting example model is evaluated in steady and transient shear forces and elongational flows and shown to offer predictions that are consistent with observed rheological behavior of typical systems of aggregating particles. Additionally, an expression for the total entropy production is also provided that allows one to judge the thermodynamic consistency and to evaluate the importance of the various dissipative phenomena involved in given flow processes. [ABSTRACT FROM AUTHOR]

The larval stage of the European fire salamander (Salamandra salamandra) inhabits both lentic and lotic habitats. In the latter, they are constantly exposed to unidirectional water flow, which has been shown to cause downstream drift in a variety of taxa. In this study, a closed artificial creek, which allowed us to keep the water flow constant over time and, at the same time, to simulates with predefined water quantities and durations, was used to examine the individual movement patterns of marked larval fire salamanders exposed to unidirectional flow. Movements were tracked by marking the larvae with VIAlpha tags individually and by using downstream and upstream traps. Most individuals showed stationarity, while downstream drift dominated the overall movement pattern. Upstream movements were rare and occurred only on small distances of about 30 cm; downstream drift distances exceeded 10 m (until next downstream trap). The simulated flood events increased drift rates significantly, even several days after the flood simulation experiments. Drift probability increased with decreasing body size and decreasing nutritional status. Our results support the production hypothesis as an explanation for the movements of European fire salamander larvae within creeks. [ABSTRACT FROM AUTHOR]

Computer-aided individual recognition of animals based on their natural markings has become an indispensable tool in ecology research. However, this is problematic in species with faint patterns. Here we test whether individually reared larvae of the European Fire Salamander (Salamandra salamandra) can be reliably recognized from images of their lateral tail patterns. We used Wild-ID software to (1) estimate the recognition uncertainty resulting from pre-processing the images, (2) quantify how pre-contrasting improves recognition, (3) assess the effect of ontogenetic pattern change on recognition until metamorphosis, and (4) test how recognition performs with larger image libraries. Our results show that discrimination of larvae is highly successful. Pre-processing did not lead to a relevant change in the recognition probability, while pre-contrasting even reduced the recognition probability. The shorter the time interval between two photos, the more readily an individual will be recognized. The overall recognition rate was 99.81%, with false rejection rates (FRR, calculated as the number of falsely rejected images divided by the number of matching attempts) amounting to 4.66, 0.77 and 0.20% for FRR1 (first image provided by Wild-ID does not match), FRR10 (none of the first ten images provided by Wild-ID matches) and FRR21 (none of the first 20 images provided by Wild-ID matches), respectively. These rates are among the lowest ever reported. The inclusion of images of 130 wild-caught larvae did not negatively affect successful individual recognition. Automated photo-identification may therefore be considered a reliable tool for fieldwork on European Fire Salamander larvae. [ABSTRACT FROM AUTHOR]

Model aluminosilicate (N‐A‐S‐H) gel systems give insight to the complex reaction occurring in alkali‐activated binders, allowing for more precise control over chemical composition and exhibiting simpler kinetics. Small angle neutron scattering, oscillatory rheology, and solid‐state NMR were used to characterize N‐A‐S‐H gel samples and relate structure, chemical composition, and rheology. Aluminum concentration was varied in the gel samples at fixed silica and sodium concentration. Past the percolation point, the gel develops in two regimes distinct in structure and rheological behavior. The first gel regime is characterized by increase in modulus and initial formation of fractal structures following a diffusion‐limited monomer‐cluster aggregation mechanism. The second gel regime at higher aluminum concentrations is characterized by a modulus plateau and structure development via reaction‐limited aggregation of existing clusters. NMR data indicate a saturation of aluminum in the network at the transition between gel regimes, which may be pH driven. Understanding the structure‐property relationships critical to formation of the N‐A‐S‐H gel can give valuable insight to the reaction mechanism in alkali‐activated binders and the influence of chemical composition on resultant structure and mechanical properties. [ABSTRACT FROM AUTHOR]

The European urodelan diversity is threatened by the recent range expansion of the chytrid fungus Batrachochytrium salamandrivorans. The fire salamander can be classified as especially sensitive as infection of individuals with this parasitic fungus usually leads to chytridiomycosis and rapid mortality. Hence, to observe effects at the population level, it is crucial to monitor population sizes and trends. The abundance of adult fire salamanders is far more difficult to estimate compared to larval stages. Therefore, population monitoring of fire salamanders focusses on the aquatic larvae. We examined abundances of larval fire salamanders in two different first-order creeks. Four different methods were compared: two simple count methods, and two abundance estimates using removal sampling and capture-mark-recapture (CMR), respectively. The results of the count methods strongly correlated with the abundance estimates. Furthermore, the results of the removal sampling correlated with the estimates using CMR data. The estimates of the CMR study should get closer to real larval abundances in the creeks compared to the estimates of the removal sampling approach. Count methods but also removal sampling analysis underestimate real larval abundances. Due to (i) the strong correlations of the results, (ii) less time and cost effort of removal sampling compared to CMR, we suggest the removal sampling method, keeping in mind that real larval population is larger. [ABSTRACT FROM AUTHOR]

The European fire salamander (Salamandra salamandra) is a widespread species that occurs in a variety of habitats throughout its range. We studied if different environmental parameters influence presence as well as abundance of larvae within different local landscape units across a more than 5,000 km² large Central European study area. This knowledge is crucial to differentiate between habitat specific absence/low abundance and externally triggered extinctions or population declines, e.g. through newly emerging infectious diseases. Within our study area, the salamander plague, caused by the invasive fungus Batrachochytrium salamandrivorans, has recently been invoked as major factor for population declines in S. salamandra. We estimated larval habitat preferences of 135 European fire salamander populations (presence-absence only), and estimated larval abundances in 85 out of them. In the entire study area, regardless of landscape units, presence of European fire salamander larvae was positively affected by low elevation, a high number of pools (preferred larval microhabitats) and a high amount of consumable macrozoobenthos in the reproduction creeks as well as a high proportion of forest cover in the surrounding terrestrial habitats. Apart from some minor differences among landscape units when they were analysed separately, we observed in many cases a positive effect of a high number of pools (11 out of 56 overall models = 20%) and, furthermore, a negative effect of a late mapping date (mainly due to larval drift caused by heavy rainfalls in early summer and metamorphosis) on larval abundances (12 out of 56 overall models = 21%). Consequently, at least in this Central European study area, which includes mountainous regions up to 700 m a.s.l. ('West- and Osteifel', 'Hunsrück'), a mainly agriculturally used lime soil plateau ('Gutland') and a river valley ('Moseltal'), these habitat preferences can be used to differentiate between habitat-caused and disease-caused absence of European fire salamanders and also population declines using the larval population. [ABSTRACT FROM AUTHOR]

Emerging infectious diseases are one of the main suggested reasons for global amphibian decline. Fungal agents play a key role. Since its introduction, the Asian pathogen Batrachochytrium salamandrivorans has driven the European fire salamander, Salamandra salamandra, to the edge of extinction in the Netherlands and caused severe population declines in Belgium and Germany. We screened 1,526 amphibians (1,431 urodelans and 95 anurans) from 50 sites in a 1,500 km² large area in Germany, south of the next known infected populations. Furthermore, we conducted a presence-absence mapping of larval salamanders in 88 randomly selected creeks and creeks where salamanders had been reported in the past using a standardized removal sampling approach. Our results revealed an expanded distribution of the pathogen in Western Germany and we could detect seven infected urodelan populations including the southernmost locality of the fungus in its exotic range. Larval salamanders were found in 54 out of 63 creeks south, but only in seven out of 25 creeks north of a highway that divides the study area. Bsal infection could mainly be detected in newts (Ichthyosaura alpestris and Lissotriton helveticus) because many previously known European fire salamander populations most likely disappeared in the affected forest regions, however, silently and without observed mass mortalities. The only detectable salamander population north of the highway was found to be Bsal-infected at high prevalence in 2019, but not from 2016 to 2018, suggesting a recent infection event. Overall, prevalence at the individual (2.6%) and population level (14%) was very low. Moreover, modelling habitat suitability in seemingly unaffected areas suggests that most reproduction creeks and surrounding land habitats in the seemingly affected area are still suitable for S. salamandra, supporting our suspicion that the absence of the species is disease-related rather than habitat related. [ABSTRACT FROM AUTHOR]

The presence of the parasitic amphibian chytrid fungus Batrachochytrium salamandrivorans (Bsal) in the Eifel Mountains, Germany, was confirmed in 2015. Since then, monitoring of selected populations of the European fire salamander (Salamandra salamandra) has been established. This species is highly sensitive to the pathogen and infection is commonly lethal for individuals within several days, which gave rise to the term 'salamander plague'. Because of the low detection probability of the terrestrial phase of the salamanders, we assessed the status of populations by monitoring the abundance of aquatic larvae as a proxy. A standardized removal sampling was conducted between 2015 and 2019 in 40 creeks in the Northern Eifel Mountains (21 sites with consistent 5-year data) and in 21 creeks in the Southern Eifel Mountains (17 sites with consistent 5-year data). While in the northern Eifel the pathogen was detected in 2015 and is known to be present since 2004, in the southern Eifel Bsal-sites has been confirmed since 2017. In both regions, the number of pools was the best fitting explanatory variable for abundances and detection probabilities of larvae. Indications for larval decline were observed in some creeks with Bsal presence while in others capture rates and larval abundances did not significantly change or sometimes even increased when Bsal was present. As a result, our data do not indicate an effect of the salamander plague to consistently and immediately causing declines in larval abundance. However, these findings remain tentative, and final conclusions should not be drawn yet. The applied removal sampling method is suggested to represent a time- and cost-effective as well as feasible means to obtain long-term population information on larval abundance in the European fire salamander. [ABSTRACT FROM AUTHOR]

The salamander plague, caused by the amphibian chytrid fungus Batrachochytrium salamandrivorans (Bsal), is one of the most devastating amphibian diseases, currently threatening the entire Western Palearctic caudate diversity with extinction. Apparently of Asian origin and recently introduced into Europe, Bsal is known from currently ca. 80 sites in the wild in four European countries. Germany is the Bsal 'hotspot', with more than half (N = 50) of all known European records to date. We here present data based on > 8,500 caudate specimens sampled for Bsal mainly via skin swabbing and quantitative real time PCR (> 3,300 since 2019). Within regions of Bsal occurrence ~ 6-7% of the studied caudates were Bsal-positive. The oldest known European record of the pathogen is from this country (2004), but a massive Bsal dispersal has only been recognized within the last five years with 17 new Bsal sites since 2019 alone. Currently, Bsal is spreading within the northern and the southern Eifel and -- since 2017 -- the Ruhr District. Most recently, the pathogen was for the first time detected in southern Germany (Bavaria) and a further range expansion is expected. A new species distribution model (SDM) of Bsal based on > 100 native and invasive records predicts suitable areas in most parts of Germany. Bsal affects all five caudate species known from these regions and has catastrophic effects on the European fire salamander (Salamandra salamandra). All affected populations in Germany (as well as Belgium and The Netherlands) have dramatically declined. While some may have become extinct due to the salamander plague, in most Bsal-positive sites European fire salamanders can still be recorded at low numbers (at least via systematic larval surveys), and at least one population seems to have recovered as currently Bsal detection remains negative. Little is known about the effect of Bsal on newts, and both prevalence and individual infection load can vary greatly over time, even within one population. However, the situation of the northern crested newt (Triturus cristatus) is alarming, as this species also undergoes declines due to Bsal invasions at some sites. Although some anurans are suggested as potential Bsal reservoirs and transmitters, we detected Bsal in only one individual of the common frog (Rana temporaria) out of 365 anurans of various species tested. Co-infection of Bsal with the related chytrid taxon Batrachochytrium dendrobatidis is known from three taxa (S. salamandra, T. cristatus, Ichthyo saura alpestris) and at four sites. The alarming data from Bsal in Germany call for immediate conservation action at all levels, including ex situ conservation. We therefore strongly support the establishment and implementation of a national Bsal Action Plan. [ABSTRACT FROM AUTHOR]

The European urodelan diversity is threatened by the recent range expansion of the chytrid fungus Batrachochytrium salamandrivorans. The fire salamander can be classified as especially sensitive as infection of individuals with this parasitic fungus usually leads to chytridiomycosis and rapid mortality. Hence, to observe effects at the population level, it is crucial to monitor population sizes and trends. The abundance of adult fire salamanders is far more difficult to estimate compared to larval stages. Therefore, population monitoring of fire salamanders focusses on the aquatic larvae. We examined abundances of larval fire salamanders in two different first-order creeks. Four different methods were compared: two simple count methods, and two abundance estimates using removal sampling and capture-mark-recapture (CMR), respectively. The results of the count methods strongly correlated with the abundance estimates. Furthermore, the results of the removal sampling correlated with the estimates using CMR data. The estimates of the CMR study should get closer to real larval abundances in the creeks compared to the estimates of the removal sampling approach. Count methods but also removal sampling analysis underestimate real larval abundances. Due to (i) the strong correlations of the results, (ii) less time and cost effort of removal sampling compared to CMR, we suggest the removal sampling method, keeping in mind that real larval population is larger. [ABSTRACT FROM AUTHOR]

The European fire salamander (Salamandra salamandra) is a widespread species that occurs in a variety of habitats throughout its range. We studied if different environmental parameters influence presence as well as abundance of larvae within different local landscape units across a more than 5,000 km? large Central European study area. This knowledge is crucial to differentiate between habitat specific absence/low abundance and externally triggered extinctions or population declines, e.g. through newly emerging infectious diseases. Within our study area, the salamander plague, caused by the invasive fungus Batrachochytrium salamandrivorans, has recently been invoked as major factor for population declines in S. salamandra. We estimated larval habitat preferences of 135 European fire salamander populations (presence-absence only), and estimated larval abundances in 85 out of them. In the entire study area, regardless of landscape units, presence of European fire salamander larvae was positively affected by low elevation, a high number of pools (preferred larval microhabitats) and a high amount of consumable macrozoobenthos in the reproduction creeks as well as a high proportion of forest cover in the surrounding terrestrial habitats. Apart from some minor differences among landscape units when they were analysed separately, we observed in many cases a positive effect of a high number of pools (11 out of 56 overall models = 20%) and, furthermore, a negative effect of a late mapping date (mainly due to larval drift caused by heavy rainfalls in early summer and metamorphosis) on larval abundances (12 out of 56 overall models = 21%). Consequently, at least in this Central European study area, which includes mountainous regions up to 700 m a.s.l. ('West- and Osteifel', 'Hunsrück'), a mainly agriculturally used lime soil plateau ('Gutland') and a river valley ('Moseltal'), these habitat preferences can be used to differentiate between habitat-caused and disease-caused absence of European fire salamanders and also population declines using the larval population. [ABSTRACT FROM AUTHOR]

The presence of the parasitic amphibian chytrid fungus Batrachochytrium salamandrivorans (Bsal) in the Eifel Mountains, Germany, was confirmed in 2015. Since then, monitoring of selected populations of the European fire salamander (Salamandra salamandra) has been established. This species is highly sensitive to the pathogen and infection is commonly lethal for individuals within several days, which gave rise to the term 'salamander plague'. Because of the low detection probability of the terrestrial phase of the salamanders, we assessed the status of populations by monitoring the abundance of aquatic larvae as a proxy. A standardized removal sampling was conducted between 2015 and 2019 in 40 creeks in the Northern Eifel Mountains (21 sites with consistent 5-year data) and in 21 creeks in the Southern Eifel Mountains (17 sites with consistent 5-year data). While in the northern Eifel the pathogen was detected in 2015 and is known to be present since 2004, in the southern Eifel Bsal-sites has been confirmed since 2017. In both regions, the number of pools was the best fitting explanatory variable for abundances and detection probabilities of larvae. Indications for larval decline were observed in some creeks with Bsal presence while in others capture rates and larval abundances did not significantly change or sometimes even increased when Bsal was present. As a result, our data do not indicate an effect of the salamander plague to consistently and immediately causing declines in larval abundance. However, these findings remain tentative, and final conclusions should not be drawn yet. The applied removal sampling method is suggested to represent a time- and cost-effective as well as feasible means to obtain long-term population information on larval abundance in the European fire salamander. [ABSTRACT FROM AUTHOR]

The salamander plague, caused by the amphibian chytrid fungus Batrachochytrium salamandrivorans (Bsal), is one of the most devastating amphibian diseases, currently threatening the entire Western Palearctic caudate diversity with extinction. Apparently of Asian origin and recently introduced into Europe, Bsal is known from currently ca. 80 sites in the wild in four European countries. Germany is the Bsal 'hotspot', with more than half (N = 50) of all known European records to date. We here present data based on > 8,500 caudate specimens sampled for Bsal mainly via skin swabbing and quantitative real time PCR (> 3,300 since 2019). Within regions of Bsal occurrence ~ 6-7% of the studied caudates were Bsal-positive. The oldest known European record of the pathogen is from this country (2004), but a massive Bsal dispersal has only been recognized within the last five years with 17 new Bsal sites since 2019 alone. Currently, Bsal is spreading within the northern and the southern Eifel and - since 2017 - the Ruhr District. Most recently, the pathogen was for the first time detected in southern Germany (Bavaria) and a further range expansion is expected. A new species distribution model (SDM) of Bsal based on > 100 native and invasive records predicts suitable areas in most parts of Germany. Bsal affects all five caudate species known from these regions and has catastrophic effects on the European fire salamander (Salamandra salamandra). All affected populations in Germany (as well as Belgium and The Netherlands) have dramatically declined. While some may have become extinct due to the salamander plague, in most Bsal-positive sites European fire salamanders can still be recorded at low numbers (at least via systematic larval surveys), and at least one population seems to have recovered as currently Bsal detection remains negative. Little is known about the effect of Bsal on newts, and both prevalence and individual infection load can vary greatly over time, even within one population. However, the situation of the northern crested newt (Triturus cristatus) is alarming, as this species also undergoes declines due to Bsal invasions at some sites. Although some anurans are suggested as potential Bsal reservoirs and transmitters, we detected Bsal in only one individual of the common frog (Rana temporaria) out of 365 anurans of various species tested. Co-infection of Bsal with the related chytrid taxon Batrachochytrium dendrobatidis is known from three taxa (S. salamandra, T. cristatus, Ichthyosaura alpestris) and at four sites. The alarming data from Bsal in Germany call for immediate conservation action at all levels, including ex situ conservation. We therefore strongly support the establishment and implementation of a national Bsal Action Plan. [ABSTRACT FROM AUTHOR]

Emerging infectious diseases are one of the main suggested reasons for global amphibian decline. Fungal agents play a key role. Since its introduction, the Asian pathogen Batrachochytrium salamandrivorans has driven the European fire salamander, Salamandra salamandra, to the edge of extinction in the Netherlands and caused severe population declines in Belgium and Germany. We screened 1,526 amphibians (1,431 urodelans and 95 anurans) from 50 sites in a 1,500 km? large area in Germany, south of the next known infected populations. Furthermore, we conducted a presenceabsence mapping of larval salamanders in 88 randomly selected creeks and creeks where salamanders had been reported in the past using a standardized removal sampling approach. Our results revealed an expanded distribution of the pathogen in Western Germany and we could detect seven infected urodelan populations including the southernmost locality of the fungus in its exotic range. Larval salamanders were found in 54 out of 63 creeks south, but only in seven out of 25 creeks north of a highway that divides the study area. Bsal infection could mainly be detected in newts (Ichthyosaura alpestris and Lissotriton helveticus) because many previously known European fire salamander populations most likely disappeared in the affected forest regions, however, silently and without observed mass mortalities. The only detectable salamander population north of the highway was found to be Bsal-infected at high prevalence in 2019, but not from 2016 to 2018, suggesting a recent infection event. Overall, prevalence at the individual (2.6%) and population level (14%) was very low. Moreover, modelling habitat suitability in seemingly unaffected areas suggests that most reproduction creeks and surrounding land habitats in the seemingly affected area are still suitable for S. salamandra, supporting our suspicion that the absence of the species is disease-related rather than habitat related. [ABSTRACT FROM AUTHOR]

We derive a statistical mechanical model for colloidal interactions mediated by polymer-like micelles (PLMs) that adsorb at the colloid surface. The model considers the end-adsorption and reversible scission of ideal chains, and is based on experimentally measurable parameters relevant to PLMs. The model predicts interparticle attractions due to micellar bridging that are stronger and longer-range than those encountered in ordinary telechelic polymers. Mapping the analytical potential onto the more familiar Double Yukawa potential allows, for the first time, accurate, a priori prediction of suspension microstructure and phase behavior when compared to experimental data for model nanoparticles dispersed in wormlike micelles over a range of solution conditions. [ABSTRACT FROM AUTHOR]

The shear induced microstructure for electrostatic and Brownian suspensions are compared using in situ small angle neutron scattering (SANS). The dispersions consist of 75 nm Stöber silica coated with 3-(trimethoxysilyl) propyl methacrylate (TPM) and have a zeta potential of -42.6 ± 4.7 mV. Neutralizing the surface charge with 0.066 M— nitric acid yields stable hard-sphere dispersions. SANS is conducted over a range of shear rates on the charge-stabilized and Brownian suspensions to test the order-disorder transition and hydrocluster mechanisms for shear thickening, and demonstrate the influence of stabilizing forces on the shear induced microstructure evolution. Through treatment of the colloidal micromechanics, shear induced changes in the microstructure are correlated to the hydrodynamic component of the shear stress and the thermodynamic component of the normal stress, i.e., the method of "Rheo-SANS" is developed. The results demonstrate that hydrocluster formation accompanies the shear thickening transition. [ABSTRACT FROM AUTHOR]

The mechanics of understanding a new application of the bracket theory of Non-Equilibrium Thermodynamics that allows for the incorporation of microstructural inertia effects within conformation tensor-based constitutive models of macroscopic material behavior is presented. Introducing inertia effects generally requires the replacement of a first order in time evolution equation for the conformation tensor by a second order one. Through the analysis of a simple damped oscillator we bring forward here the close connection to the structural dissipation brackets present in the two cases, with the weights being inverted as one transitions from the inertialess to the inertial description. Moreover, one may also describe inertial effects in material flow in certain situations through a simple modification of the first order evolution equation for the conformation tensor, which consists of adding a new non-affine term that couples the conformation and the vorticity tensors, as detailed in a recent publication (P. M. Mwasame, N. J. Wagner and A. N. Beris, Phys. Fluids, 30 (2018), 030704). As shown there, when applied to the low particle Reynolds flow of dilute emulsions, this reduced inertial flow model provides predictions consistent with literature-available microscopically based asymptotic results. [ABSTRACT FROM AUTHOR]

Stabilized-emulsions often undergo Ostwald ripening owing to the higher solubility of the smaller droplets. Their rheological properties are a direct result of the interplay between their microstructure and flow, which in turn affect their processing as well as their applications. In a recent study [Mwasame et al., "On the macroscopic modelling of dilute emulsions under flow," J. Fluid Mech. 831, 433–473 (2017)], the use of a unit determinant conformation tensor to represent morphological changes has been advanced within the context of a thermodynamically consistent theory for a dilute monodisperse emulsion. The resulting model was validated against previously developed asymptotic theory that was also used to obtain all model parameters. In the present work, the first key innovation is to show how this theory can be extended to allow for multiple conformation tensors, subject to a single joint constraint originating from the mass conservation of the dispersed phase, in order to allow for the representation of dilute polydisperse emulsions undergoing Ostwald ripening. The second enabling innovation of this work is to show how to introduce correct dissipative terms into the dissipation bracket to account for mass transfer processes. The approach is illustrated for the particular case of a bidisperse emulsion. The model illustrates how multiple transport phenomena and thermodynamic effects can be seamlessly combined within a thermodynamically consistent approach. This work allows for not only the coexistence of a bimodal population of droplets but also the evaluation of their deformability and effective rheology in the presence of Ostwald ripening as the largest size droplets increase in mass at the expense of the smaller ones. [ABSTRACT FROM AUTHOR]

Studies the effects of colloidal interactions on the kinetics and extent of adsorption using a dynamic simulation of colloidal adsorption. Diffusion by Brownian dynamics accounted for by the simulation; Characterization of particle-particle and particle-surface interactions; Classes of charged colloidal particles considered.

Nonequilibrium Brownian dynamics simulations are used to study the effect of polydispersity on the thermodynamics, rheology, microstructure, and shear-induced disorder–order transition in suspensions of charged colloids. Approximately 43 000 particles with 2000 different components of a discretized Schulz distribution at polydispersities from 0% to 30% are simulated on a massively parallel computer. Recent advances in the integral equation theory for polydisperse suspensions are tested and verified with respect to both structure and equilibrium mechanical properties. The low shear rate rheology for both monodisperse and polydisperse suspensions is found to be well represented by the Ree–Eyring model. At higher shear rates an ordered ‘‘string’’ phase is shear induced for low polydispersities (<10%). Increasing the polydispersity further (>=20%) inhibits the ordering, suggesting the existence of a critical polydispersity beyond which a colloidal suspension cannot be induced into an ordered state by shearing. The validity of a generalized, nonequilibrium Stokes–Einstein relationship for polydisperse colloids is also investigated. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The simple shearing of a suspension of charge-stabilized, colloidal particles close to the melting line is investigated by massively parallel, nonequilibrium Brownian dynamics (NEBD) simulation. The suspension undergoes a discontinuous transition from a distorted fluid structure to an ordered ‘‘string’’ phase. Comparisons between simulations of 43 000, 4725 particles, and previous NEBD work on ≤500 particles proves that shear-induced ordering is not an artifact of the small system sizes. We also show that the shear-rate dependence of the rheological properties obtained from NEBD is different than those obtained from nonequilibrium molecular dynamics (NEMD), a consequence of the solvent damping not being present in NEMD. The validity of the Ree–Eyring model for viscosity and the stress-optic law for colloids are tested. Further, a type of generalized Stokes–Einstein relationship is discovered for systems under shear. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The two-particle correlation function is related to the structure factor by an integral transform and serves as an important connection between suspension microstructure, scattering experiments, and macroscopic properties. The nonequilibrium structure factor for a shearing colloidal suspension of spherical particles is expanded in spherical harmonics. Through this expansion, we demonstrate formal relationships between the experimentally accessible static structure factor, bulk stresses, and optical dichroism and birefringence, demonstrating that a limited number of expansion terms are required to characterize the suspension rheology. Low shear limiting theories are expressed in terms of this expansion, demonstrating the utility of the expansion for comparison of experimental measurements of nonequilibrium structure factors to theoretical predictions. Although flow birefringence and the thermodynamic shear stress are calculated as weighted integrals over the nonequilibrium microstructure in the low shear limit, no simple stress-optical coefficient is found. The expansion is proposed as a consistent methodology for analysis of experimental data and presentation of theoretical predictions, providing a means of interpreting rheo-optical data. [ABSTRACT FROM AUTHOR]

Structure measurements of a suspension of charged polystyrene spheres with significant polydispersity (16%) are reported for a wide range of particle and added salt concentrations and scattering wave vector. Small angle neutron scattering yielded the structure factors of concentrated samples that have had extensive rheological characterization. A Schulz distribution was used as a model of the particle size distribution to reduce the intensity data and as a basis for the theoretical fits of the structure factors. Static light scattering measurements yielded the structure factors of diluted, deionized samples. Dynamic light scattering was also performed to study the relaxation of these structures. These measured structures were fit with a recent theory that accounts for both size and charge polydispersity in the suspension. These results and the previous extensive, rheological investigations and physical characterization yield a complete data set on a well-characterized, model system that can be used to test theories of the statics and dynamics of polydisperse colloidal suspensions. [ABSTRACT FROM AUTHOR]

Optical measurements were used to detect structural anisotropy in concentrated dispersions over a range of Peclet numbers. Silica spheres of 49 and 130 nm radii with grafted octadecyl chains were dispersed in cyclohexane at volume fractions from 0.1 to 0.4. The apparatus consisted of a Couette cell with the dispersion in the annulus probed by a HeNe laser beam parallel to the axis of rotation. The dichroism and birefringence of the transmitted beam varied linearly with shear rate at low Peclet numbers with an orientation coincident with the principle direction of shear. Increasing the Peclet number, by increasing the particle size, produced a nonlinear response with the orientation tending to align in the direction of flow. A theory coupling the nonequilibrium microstructure under shear to the optical properties of the suspension enables direct interpretation of the dichroism. Comparison of sample dichroism calculations for two different forms of the theory demonstrates that the optical technique can be used to discriminate between theories which predict the microstructure. [ABSTRACT FROM AUTHOR]

Knowledge of the nanoscale distribution of proteins in chromatographic resins is critical to our mechanistic understanding of separations performance. However, the nano- to mesoscale architecture of these materials is challenging to characterize using conventional techniques. Small-angle neutron scattering was used to probe (1) the nano- to mesoscale structure of chromatographic media and (2) protein sorption in these media in situ with protein-scale resolution. In particular, we characterize the effect of the architecture of cellulose-based and traditional and dextran-modified agarose-based ion-exchange resins on the nanoscale distribution of a relatively small protein (lysozyme) and two larger proteins (lactoferrin and a monoclonal antibody) at different protein loadings. Traditional agarose-based resins (SP Sepharose FF) can be envisioned as comprising long, thin strands of helical resin material around which the proteins adsorb, while higher static capacities are achieved in dextran-modified resins (SP Sepharose XL and Capto S) due to protein partitioning into the increased effective binding volume provided by the dextran. While protein size is shown not to affect the underlying sorption behavior in agarose-based resins such as SP Sepharose FF and XL, it plays an important role in the cellulose-based S HyperCel and the more highly cross-linked agarose-based Capto S, where size-exclusion effects prevent larger proteins from binding to the base matrix resin strands. Based on the data, we propose that entropic partitioning effects such as depletion forces may drive the observed protein crowding. In general, these observations elucidate the structure and point to the mechanism of protein partitioning in different classes of chromatographic materials, providing guidance for optimizing their performance. [ABSTRACT FROM AUTHOR]

In situ measurements are an increasingly important tool to inform the complex relationship between nanoscale properties and macroscopic material measurements. Knowledge of these phenomena can be used to develop new materials to meet the performance demands of next generation technologies. Conductive complex fluids have emerged as an area of research where the electrical and mechanical properties are key design parameters. To study the relationship between microstructure, conductivity, and rheology, we have developed a small angle neutron scattering (SANS) compatible Couette rheological geometry capable of making impedance spectroscopy measurements under continuous shear. We have also mounted this geometry on a commercial strain controlled rheometer with a modified forced convection oven. In this manuscript, we introduce the simultaneous measurement of impedance spectroscopy, rheological properties and SANS data. We describe the validation of this dielectric RheoSANS instrument and demonstrate its operation using two systems—an ion gel comprising Pluronic® surfactant and ionic liquid, ethyl-ammonium nitrate, and poly(3-hexylthiophene) organogel prepared in a mixture of hexadecane and dichlorobenzene. In both systems, we use this new measurement capability to study the microstructural state of these materials under two different protocols. By monitoring their dielectric rheology at the same time as the SANS measurement, we demonstrate the capacity to directly probe structure-property relationships inherent to the macroscopic material response. [ABSTRACT FROM AUTHOR]

Environmental contamination is suggested to contribute to amphibian population declines. However, the effects of a contaminant on a particular amphibian species can differ among populations. The authors investigated the toxic effects of 2 herbicide formulations on different populations and on representative developmental stages of the European common frog (Rana temporaria). Larvae from forest populations were more sensitive to a commonly used glyphosate-based herbicide compared with individuals from agrarian land. Median lethal concentrations correlated with measured glyphosate levels in the breeding ponds, which may be a sign of evolved tolerances. The reverse result was observed for a less commonly used cycloxydim-based herbicide. Effects of the glyphosate-based herbicide were stronger for earlier larval stages compared with later larval stages. Hence, applications in early spring (when early larvae are present in breeding ponds) pose greater risk concerning acute toxic effects on R. temporaria. With regard to late larval stages, short exposure (96?h) of prometamorphic larvae prolonged time to metamorphosis, but only at the highest test concentration that did not significantly induce mortality. This could be due to impairment of the thyroid axis. Notably, nearly all test concentrations of the 2 herbicides provoked growth retardation. Further research on how evolved or induced tolerances are acquired, actual contamination levels of amphibian habitats, and potential endocrine effects of glyphosate-based herbicides is necessary. [ABSTRACT FROM AUTHOR]

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]

Novel measurements of the spatiotemporal microstructure of a continuous shear thickening colloidal suspension under shear cessation and reversal using small angle neutron scattering in a 1–2 shear cell are presented for moderate to high Péclet numbers. In the shear cessation experiments from high Péclet shear flow, two-step relaxation mechanism is found. Particles first readily diffuse on a characteristic timescale of single particle Brownian motion, followed by slower relaxation dynamics on a timescale of short-time self-diffusion when caging effects start dominating. In the shear reversal experiment, the unchanged scattering intensity and the quick flip in anisotropic structure around the shear thickened state suggest the persistence of hydroclusters without transitioning through the equilibrium structure, at least in a time resolution of 0.01 s. Access to the time evolution of microstructure provides valuable insights into the spatiotemporal details of interparticle interactions governing colloidal suspension rheology, such as Brownian, hydrodynamic, and nanotribological forces. [ABSTRACT FROM AUTHOR]

The present study develops a fully consistent extension of the approach pioneered by Farris ["Prediction of the viscosity of multimodal suspensions from unimodal viscosity data," Trans. Soc. Rheol. 12, 281-301 (1968)] to describe the viscosity of polydisperse suspensions significantly improving upon our previous model [P. M. Mwasame, N. J. Wagner, and A. N. Beris, "Modeling the effects of polydispersity on the viscosity of noncolloidal hard sphere suspensions," J. Rheol. 60, 225-240 (2016)]. The new model captures the Farris limit of large size differences between consecutive particle size classes in a suspension. Moreover, the new model includes a further generalization that enables its application to real, complex suspensions that deviate from ideal non-colloidal suspension behavior. The capability of the new model to predict the viscosity of complex suspensions is illustrated by comparison against experimental data. [ABSTRACT FROM AUTHOR]

The microstructure of mixtures of deuterated water in the ionic liquid [C4mim][BF4] is investigated by small-angle neutron scattering (SANS) measurement. In the salt-rich region, water dissolves in the ionic liquid up to 0.7 mole fraction, whereupon distinct, nanometer-sized water clusters are observed. These water nanoclusters increase in size with increasing water addition while the mole ratio of water dissolved into the ionic liquid nanostructure increases from 2 to 4. These results provide direct confirmation for recent simulations as well insight into the source of nonidealities in some thermophysical and transport properties (e.g., density and viscosity) of salt-rich aqueous mixtures reported in the literature. [ABSTRACT FROM AUTHOR]

The microstructure of mixtures of deuterated water in the ionic liquid [C4mim][BF4] is investigated by small-angle neutron scattering (SANS) measurement. In the salt-rich region, water dissolves in the ionic liquid up to 0.7 mole fraction, whereupon distinct, nanometer-sized water clusters are observed. These water nanoclusters increase in size with increasing water addition while the mole ratio of water dissolved into the ionic liquid nanostructure increases from 2 to 4. These results provide direct confirmation for recent simulations as well insight into the source of nonidealities in some thermophysical and transport properties (e.g., density and viscosity) of salt-rich aqueous mixtures reported in the literature. [ABSTRACT FROM AUTHOR]

Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. [ABSTRACT FROM AUTHOR]

he present study develops an extension of the approach pioneered by Farris [Trans. Soc. Rheol. 12, 281-301 (1968)] to model the viscosity in polydisperse suspensions. Each smaller particle size class is assumed to contribute to the suspension viscosity through a weighting function in two ways: first, indirectly, by altering the background viscosity, and second, directly, by increasing the contribution of the larger particles to the suspension viscosity. The weighting functions are developed in a consistent fashion as a power law with the exponent, h, a function of the relative volume fraction ratio and the base, g, a function of the solid particle size ratio. The model is fit to available theoretical and experimental results for the viscosity of several binary suspensions and shows good to excellent agreement depending on the functions g and h chosen. Once parameterized using binary suspension viscosity data, the predictive capability to model the viscosity of arbitrary continuous size distributions is realized by representing such distributions with equivalent ternary approximations selected to match the first six moments of the actual size distribution. Model predictions of the viscosity of polydisperse suspensions are presented and compared against experimental data. [ABSTRACT FROM AUTHOR]

The shear flow of non-Brownian glass spheres suspended in a concentrated colloidal dispersion that exhibits non-Newtonian rheology is investigated. At low volume fractions, the addition of non-Brownian spherical particles to the colloidal dispersion leads to an increase in the steady shear viscosity as well as the dynamic moduli. The flow curves of these suspensions are qualitatively similar to the suspending colloidal dispersion medium, and as such, in this semidilute regime, the suspension data can be shifted on to that of the colloidal dispersion medium at constant shear stress with shift factors comparable to those predicted for spherical particles in a Newtonian fluid. At higher volume fractions of non-Brownian spheres, the shear thickening power law exponent increases with the addition of non-Brownian particles. This increase in the shear thickening power law exponent is shown to be consistent with the effects of confinement on the shear thickening colloidal dispersion by the larger non-Brownian particles. [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]

SANS directly measures the structure of protein-surfactant complexes in bulk solution and thus can reliably evaluate the surfactant binding to a protein. However, there are concerns of protein stability that can be caused either by protein-protein interactions or by the surface of prefilled syringes that are usually siliconized and cause proteins to denature at these hydrophobic oil-water interfaces. [Extracted from the article]

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]

The rheology and three-dimensional microstructure of a concentrated viscoelastic solution of the triblock copolymer poly(ethylene oxide)106-poly(propylene oxide)6 8-poly(ethylene oxide)106 (Pluronic F127) in the protic ionic liquid ethylammonium nitrate are measured by small angle neutron scattering (SANS) under flow in three orthogonal planes. This solution's shear-thinning viscosity is due to the formation of two-dimensional hexagonal close-packed (HCP) sliding layer structure. Shear-melting of the crystalline structure is observed without disruption of the selfassembled micelles, resulting in a change in flow properties. Spatially resolved measurements in the 1-2 plane reveal that both shear-melting and sliding are not uniform across the Couette gap. Melting and recrystallization of the HCP layers occur cyclically during a single large amplitude oscillatory shear (LAOS) cycle, in agreement with the "stick-slip" flow mechanism proposed by Hamley et al. [Phys. Rev. E 58, 7620-7628 (1998)]. Analysis of 3D "structural" Lissajous curves show that the cyclic melting and sliding are direct functions of the strain rate amplitude and show perfect correlation with the cyclic stress response during LAOS. Both viscosity and structural order obey the Delaware-Rutgers rule. Combining rheology with in situ spatiotemporally resolved SANS is demonstrated to elucidate the structural origins of the nonlinear rheology of complex fluids. [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]

Reversible shear thickening is common in concentrated dispersions of Brownian hard-spheres at high-shear rates. We confirm the existence of a well-defined colloidal shear-thickened state through experimental measurements of the shear stress and the first and second normal stress differences in the shear-thickened state as a function of the particle volume fraction for a model dispersion of near hard-spheres. The shear stress and normal stress differences are observed to grow linearly with the shear rate in the shear-thickened state and both normal stress differences are observed to be negative. Our experimental results show the shear-thickened state of colloidal dispersions can be described by three material properties--the shear viscosity and first and second normal stress difference coefficients--that are a function of the volume fraction. All three material properties are found to diverge with a power law scaling as ... close to maximum packing, &#934max, which is found to be 0.54 ± 0.01. We find ηr,sts>γ2,sts>γ1,sts. These results are consistent with theoretical predictions for shear thickening by hydrocluster formation and quantitatively comparable to Stokesian Dynamics simulations. We further postulate and show that these material properties are consistent with those measured for non-Brownian suspensions. [ABSTRACT FROM AUTHOR]

The short-time diffusivity of dicolloid particles as a function of particle volume fraction ɸ from 0.01 ≤ ɸ ≤ 0.6 is measured using diffusing wave spectroscopy. The diffusivities of symmetric and asymmetric dicolloids are compared with similarly sized spheres. The short-time diffusivity is independent of salt concentration and decreases with increasing volume fraction for both spheres and asymmetric dicolloids. Symmetric dicolloids have a higher diffusivity than spheres at similar volume fractions. This difference is accounted for by rescaling the dicolloid volume fraction based on the ratio of the random close-packing volume fractions of spheres and dicolloids. Finally, a useful method is provided for calculating the diffusivity of symmetric dicolloid particles of arbitrary aspect ratio based on the calculated hydrodynamic resistance of Zabarankin [Proc. R. Soc. A 463, 2329 (2007)]. [ABSTRACT FROM AUTHOR]

Open-ended coaxial line probes (OCs) are systematically analyzed by means of numerical 3-D finite element calculations in combination with experimental investigations for microwave dielectric spectroscopy on fine grained soils. The probes, based on conventional coaxial lines and connectors (N, SMA), are broadband characterized in the frequency range from 1 MHz to 10 GHz. The sensitive region for dielectric measurements is ±7-mm lateral and 7-mm perpendicular to the midpoint of the sensor aperture. The spatial spreading of the sensitive zone is stable for the investigated low-loss and high-loss strongly dispersive standard liquids, as well as the saturated and unsaturated soils. Dielectric spectra are determined based on a bilinear relationship between effective permittivity and complex reflection coefficient of the probe after probe-calibration with known standards. The mean relative error of the real part of the complex permittivity from 100 MHz to 10 GHz is smaller than 3.5% and is less than 10% for the imaginary part. A lower limit of the measurement range of 50 MHz with the used procedure and materials is suggested. Complex effective permittivity of saturated fine-grained soils is determined with the developed probes and procedure. The soil dielectric spectra were analyzed with a broadband relaxation model, as well as a novel, coupled hydraulic-dielectric mixture approach. The results demonstrate the suitability of the investigated OCs for the determination of high resolution soil dielectric spectra. [ABSTRACT FROM AUTHOR]