Biology and ecology of the non-indigenous goby Acentrogobius pflaumii (Bleeker 1853) in the Swan-Canning Estuary

Non-indigenous species can have significant deleterious impacts on the ecosystems in which they become established. Following the recent establishment of the Striped Sandgoby Acentrogobius pflaumii in the Swan-Canning Estuary, south-western Australia, a study was initiated to determine its spatial and temporal distribution and biological characteristics. Although A. pflaumii was not recorded in the coarse sandy sediment present in the nearshore, shallow waters of the estuary, substantial numbers were recorded on soft muddy sediments in the deeper waters, where it comprised 55% of the total number of gobies. While A. pflaumii dominated the gobiid fauna in Lower Melville Water (~98%), its contributions declined progressively upstream, indicating a preference for waters with a salinity close to that of full strength sea water. Size and age compositions determined that the oldest individual was 3.9 years old and 89 mm in total length, but that the population is dominanted by 1+ individuals. Population mortality and turn-over rates are therefore likely to be very high. Both males and females attained > 87% of their asymptotic lengths (L∞) of 74.9 and 69.3 mm, respectively, during the first year of life, which is characteristic of smaller, shorter-lived species of fish. The results from gonadosomatic indices and the histological examination of gonads suggest that A. pflaumii is able to spawn throughout most of the year, with a peak from November to February. The presence of mature, spawning and depleted gonads in A. pflaumii suggests that this species spawns within the Swan-Canning Estuary. Acentrogobius pflaumii can be thus considered an estuarine & marine species like Favonigobius lateralis. As A. pflaumii attains high densities over a relatively large part of the estuary and can breed within the system, it is likely to be a permanent resident and further work is needed to determine its impact on the native gobiid fauna

Rheology of the cetyltrimethylammonium tosilate-water system. 2. Linear viscoelastic regime

In this work, the linear viscoelastic properties of the cetyltrimethylammonium tosilate (CTAT)-water system are examined in detail. This system forms elongated micelles at low and intermediate concentrations, and it yields a hexagonal phase above 27 wt % CTAT at 25 �C. Rheological behavior at low frequencies in a small-amplitude oscillatory shear experiments or at long times in stress relaxation measurements is governed by a single dominant relaxation time, although deviations from the limiting slope of the elastic modulus in the terminal region are observed at high CTAT concentrations. For higher frequencies, however, there is an additional mechanism whose dependence on frequency is analyzed with several rheological models. Analysis of data in terms of the theory of Cates demonstrates that the system consists of flexible micelles in the slow-breaking limit and it exhibits a constant entanglement density along the whole micellar region, even though the average micellar length decreases monotonically with concentration. Under these conditions, reptation speed up by the kinetics process of breaking and re-forming is the controlling relaxation mechanism

Thermal transitions and state of water in binary mixtures of water and n-decanephosphonic acid or its sodium salts

The state of water and several transitions were examined in the systems n-decanephosphonic acid (DPA)-water and the sodium salts of DPA-water. Temperature - composition phase diagrams are reported. The results show that several liquid crystalline phases plus isotropic liquid, and two solid phases (a waxy solid phase and a crystalline phase) are formed. Several types of water were detected: bulk-like water, interfacial water and hydration water

Length of the Core Forming Block Effect on Fusion and Fission Dynamics at Equilibrium in PEO–PPO–PEO Triblock Copolymer Micelles in the Spherical Regime

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Dynamics of worm-like micelles: The Cox-Merz rule

The viscoelastic behaviour of worm-like micelles in small-amplitude oscillatory, steady simple shear and uniaxial extensional flows are analyzed with a model that couples the Oldroyd-B constitutive equation with a kinetic equation that accounts for the structural changes induced by the flow. In some cases, the constitutive equation predicts a viscoelastic behaviour that is consistent with the Cox-Merz rule. Departures from this rule are also predicted. Experimental data obtained for two worm-like micellar systems indicate that in these solutions, the Cox-Merz rule is not usually followed, in agreement with the predictions of our model. In uniaxial extensional flow, the model predicts a strain hardening in the extensional viscosity at low extensional rates and a strain-thinning at high extensional rates. © 2002 Elsevier Science B.V. All rights reserved

Kinetics of the sphere-to-rod like micelle transition in a pluronic triblock copolymer

The kinetics of the sphere-to-rod transition was studied in aqueous micelle solutions of triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) pluronic P103 (PEO17PPO 60PEO17). This transition was triggered by a temperature jump from the sphere phase to the rod phase and monitored with dynamic light scattering. The combination of the scattering intensity and the hydrodynamic radius were used to show that the micelles grow steadily as rods throughout the growth process. The transition was found to exhibit a single exponential behavior even in the case of large deviations from equilibrium. The linear increase in the decay rate with increasing copolymer concentration shows that the transition is dominated by a mechanism involving fusion and fragmentation of proper micelles. The decays of the sphere-to-rod transition were simulated for two pathways: random fusion fragmentation and successive addition of spherical micelles to rods. We show that micelle growth most likely occurs via random fusion-fragmentation. The second order rate constant for fusion and the fragmentation rate are calculated for the case of random fusion-fragmentation. � 2012 American Chemical Society

Response of rodent assemblages to change in habitat heterogeneity in fruit-oriented nopal orchards in the Central High Plateau of Mexico

The nonlinear viscoelastic behavior of the cetyltrimethylammonium p-toluenesulfonate (CTAT)-water system is investigated in steady and unsteady shear flow as a function of surfactant concentration and temperature. A rheo-optical study which includes measurements of dichroism, birefringence, and turbidity under flow at various shear rates is also discussed. The shear viscosity data in steady shear agree with the complex viscosity in the limit of low deformation rates. For moderate deformation rates, in the shear thinning region, the Cox-Merz rule is not followed. In all cases, a limiting stress or plateau stress was observed at shear rates that exceed one-half of the reciprocal of the main relaxation time [(2?d)-1]. At the stress plateau, the micellar solution most likely undergoes an isotropic-to-nematic phase transition induced by shear. However, our results do not conclusively exclude the possibility of a constitutive instability with respect to shear banding, in which simultaneous shear rates coexist under controlled stress experiments. In unsteady shear flow, CTAT-water micellar solutions exhibit a slow transient behavior in which the system achieves steady state in starting up experiments after tens to hundreds of Maxwell relaxation times. This is consistent with the existence of shear banding. Metastable branches are also observed in thixotropic loops produced under exponential shear. The time scale of this branch coincides with that of the inception of shear flow just before the overshoot peak. Moreover, the system exhibits a quasilinear rheological behavior at long times characterized by an exponential relaxation with a single time constant. A simple model consisting of the co-deformational Maxwell constitutive equation and a kinetic equation for construction and destruction of structure is proposed to predict distinct features of the complex rheological behavior of the elongated micellar solutions. " 1999 American Chemical Society.",,,,,,,,,"http://hdl.handle.net/20.500.12104/44265","http://www.scopus.com/inward/record.url?eid=2-s2.0-0033514853&partnerID=40&md5=0f34d13bd8a3c61b19e114c3c7ee82b

Rheology of cetyltrimethylammonium tosilate-water system. 1. Relation to phase behavior

The partial phase behavior of CTAT/water is investigated here as a function of temperature by WAXS, DSC, polarizing microscopy, conductometry, 1H-NMR, and FTIR spectroscopy. Oscillatory strain and temperature sweeps are also reported. The Krafft temperature (TK) of CTAT/water is 23�C. Below this value, triclinic crystals of CTAT coexist with an isotropic solution. Above TK and at low concentrations, spherical micellar solutions are Newtonian and exhibit low viscosities. At higher concentrations (ct), cylindrical micelles form and viscosity increases dramatically with CTAT concentration, but no elastic effects are noticed. When micelles are long enough to entangle (0.9-27 wt % at 25�C), clear viscoelastic solutions form. At higher concentrations and up to 47 wt %, an hexagonal phase appears. This phase exhibits yield stress and viscoelasticity. At higher concentrations, a nonelastic, viscous solid paste forms. Micellar solutions and hexagonal phase depicts three regimes of viscoelasticity with temperature. These regimes are bounded by Tk and by the temperature (T?) at which the system exhibits its main relaxation time. T? moves to lower temperatures as CTAT concentration increases indicating that the main relaxation time decreases upon increasing concentration. � 1995 American Chemical Society

Aqueous foams and emulsions stabilized by mixtures of silica nanoparticles and surfactants: A state-of-the-art review

In the last years, mixtures of silica nanoparticles and surfactants have been widely and successfully used to stabilize a multiplicity of aqueous foams and emulsions with current and potential applications in the engineering processes. The physicochemical properties and large-scale industrial production of silica nanoparticles, as well as the practical and cheap methods offered by surfactants to modify the nanoparticles' wettability, are the main reasons for the silica nanoparticle-surfactant pair to be an effective combination on the stabilization of both aqueous foams and emulsions. This state-of-the-art review aims to offer a well-defined picture of the contemporary research on foams and emulsions (oil-in-water, water-in-oil, and the particular case of the bicontinuous ones) stabilized by mixtures of silica nanoparticles and surfactants (cationic, anionic, nonionic, and zwitterionic) featuring the top results and outlining future research in the area. Attention is paid to the processes and materials where the foams and emulsions discussed are present. The function of silica nanoparticles-surfactants synergy on stabilizing foams and emulsions is also discussed

Temporal evolution of the size distribution during exchange kinetics of pluronic P103 at low temperatures

The micellar dynamics of many (PEO-PPO-PEO) triblock copolymers have been extensively investigated throughout the past decade using ultrasonic relaxation or temperature jump experiments. These methods primarily use the total scattering intensity to quantify the exchange mechanisms, and these results are then interpreted to get an idea about temporal evolution of the micelle size and size distribution. In this paper, we present experiments where we directly measure the size of the micelles and the size distribution during the exchange kinetic of the pluronic triblock copolymer P103. Solutions of the commercial P103 surfactant form premicelle aggregates in the proximity of the critical micelle temperature and proper micelles at high temperatures. The kinetics of evolution from aggregates to proper micelles is investigated using dynamic light scattering after a temperature jump. The temporal evolution of the scattering intensity and the average size as well as the size distribution were used to discuss the possible exchange mechanisms. � 2009 American Chemical Society