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Here, we describe a pedagogical approach that combines didactics with active learning to facilitate integration across physiological systems in a team-taught, graduate-level physiology course. We covered the major physiological systems, with each system preceded by an overview of its evolution/ontogeny to provide a broader perspective. Lectures provided a framework for integration by giving examples of how each system interacted with systems that preceded and followed. In lieu of a final exam, the course culminated in capstone presentations by small groups to promote student-centered learning of integrative physiology. At the beginning of the semester, students were assigned to groups; each group chose from predetermined topics. This allowed them to accumulate information throughout the semester and required them to attend to lecture content to assess how the material applied to their topic, thereby facilitating learning and retention. Faculty were deliberate in choosing material that was presented in each system, and material that was strategically omitted, establishing “gaps” that students filled in their capstone presentations. The final week was dedicated to student preparation for their presentations, which promoted peer-to-peer teaching and problem solving by the group, assisted by faculty as necessary. Capstone presentations demonstrated students’ mastery of basic physiological principles and their ability to integrate among physiological systems, and they rated capstone presentations highly in helping with integration and critical thinking. Thus students showed a better understanding of systems physiology and the importance of integration across systems in normal function and in responding to homeostatic challenges.

Results of an extensive study of dynamic polarized (VV) and depolarized (VH) Rayleigh–Brillouin light scattering in Quinoline as a function of temperature are presented. The VV spectrum is analyzed by taking into account the fine structure (shear dip) of the VH spectrum. The hypersound velocity u ( T ) and the Landau–Placzek ratio γ ( T ) have been calculated from the frequency shift of the Brillouin lines and the ratio of the integrated intensities of the non-shifted Rayleigh line to the two Brillouin lines. Under the conditions of high-purity and long equilibration times, the temperature variations of both u ( T ) and γ ( T ) show two reproducible anomalies centered at about 17 and 42 °C. We discuss an interpretation of the anomalies based on local structure changes, and possible relations of these anomalies to liquid–liquid phase transitions in equilibrium liquids.

Time-resolved fluorescence emission anisotropy ratios of carbazolyl groups incorporated into polystyrene chains in polyethyleneoxide(PEO)/1,2-dichloroethane mixtures have been measured by the single photon counting method. The fluorescence depolarization method is very excellent to clarify various dynamical modes of polymer chains, and many theoretical and experimental researches have so far been reported in the field of polymer chain dynamics. However there are few reports about the dynamics on the polymer side chain, because the dynamical mechanism of the polymer side chain is very complicated. In this report we tried to analyze the dynamical modes of the polymer side chains by the fluorescence depolarization method. Five dynamical modes of a polymer chain based on the Woessner model were estimated by our original analytical technique `χ2-map method'. The value of each mode of a polymer side chain was discussed above the overlap concentration (C*) of PEO and the micro-environments were clarified in the vicinity of the chromophore attached to the polymer side chain.

The formation of closed-compact multi-lamellar droplets obtained upon shearing both a lamellar phase (Lα) and a two-phase–separated lamellar-sponge (Lα-L3) mixture is investigated as a function of the shear rate , using small-angle light scattering (SALS) and cross-polarized optical microscopy. In both systems the formation of droplets occurs homogeneously in the cell at a well-defined wave vector qe 1/3 via a strain-controlled process. These results suggest that the formation of droplets may be monitored in both systems by a buckling instability of the lamellae as predicted from a recent theory.

In the 1980s, the mechanism of local motions of polymer chain was discussed theoretically and experimentally by many researchers. Finally, the intermittent motion model was proposed with respect to the measurements of emission anisotropy decay curves of a chromophore incorporated into a polymer main chain in dilute polymer solutions. The relationship between orientational auto-correlation function type based on power law and measured decay curves was discussed in these reports. The local motion of anthryl groups end-capped polystyrene (APSA) was measured in various polystyrene/di-n-butyl phthalate mixtures by using the fluorescence depolarization method. The intermittent motion model for local motions of polymer segments is modified in order to apply to both dilute and semi-concentrated polymer solutions. The model predicts that the orientational auto-correlation function will be given by the KWW function when the segment–solvent collision is effective on the relaxation process. On the other hand, the hyperbolic function will be observed when the segment–segment collision becomes effective. It was found that measured decay curves in dilute and concentrated polymer solutions were well represented by the KWW function and the hyperbolic function, respectively. The result implies the fact that modified intermittent motion model is in good agreement with the experimental data.

We present a lattice model based on two n→0 spin vectors, capable of treating the thermodynamics of living networks in micellar solutions at any surfactant concentration. We establish an isomorphism between the coupling constants in the two spin vector Hamiltonian and the surfactant energies involved in the micellar situation. Solving this Hamiltonian in the mean-field approximation allows one to calculate osmotic pressure, aggregation number, free end and cross-link densities at any surfactant concentration. We derive a phase diagram, including changes in topology such as the transition between spheres and rods and between saturated and unsaturated networks. A phase separation can be found between a saturated network and a dilute solution composed of long flexible micelles or a saturated network and a solution of spherical micelles.

Arginine vasopressin (AVP) increases water permeability in the collecting duct of the nephron via activation of adenylyl cyclase. Alpha-2 (alpha2) agonists inhibit AVP-stimulated water permeability via binding to alpha2 adrenoceptors that have been divided into 3 subtypes- alpha2A, alpha2B, and alpha2C. Some biological effects mediated by alpha2 agonists result from nonadrenergic imidazoline receptors that exist in the rat kidney. Thus, alpha2-inhibition of AVP-stimulated water permeability in the rat collecting duct could be caused by imidazoline receptors. The purpose of this study was to test agonists and antagonists selective for alpha2 and imidazoline receptors on AVP-stimulated water permeability in the rat inner medullary collecting duct (IMCD). Some experiments were conducted where water permeability was stimulated by a nonhydrolyzable analog of adenosine 3', 5'-cyclic monophosphate (cAMP). Agonists included dexmedetomidine, clonidine, oxymetazoline, agmatine and rilmenidine. The latter two are selective imidazoline agonists. Antagonists included yohimbine, RX821002, atipamezole, prazosin, WB4101, idazoxan, and BU239. Prazosin and WB4101 demonstrate selectivity for the alpha2B and alpha2C subtypes, respectively, and oxymetazoline and RX821002 are selective for the alpha2A subtype. BU239 is selective for imidazoline receptors. Wistar rat terminal IMCDs were isolated and perfused to determine the osmotic water permeability coefficient (Pf). All agonists except agmatine inhibited AVP-stimulated Pf. Inhibition by rilmenidine indicated a different mechanism of action from other agonists. Dose-response data show dexmedetomidine to be the most potent inhibitor. Oxymetazoline and clonidine inhibited cAMP-stimulated Pf indicating that the mechanism involves postcAMP cellular events. It was reported previously that dexmedetomidine inhibits cAMP-stimulated Pf (1). All antagonists except prazosin and WB4101 reversed alpha2-inhibition of AVP-stimulated Pf. BU239 was effective at 1 microM but not at 100 nM. Results suggest that alpha2A adrenoceptors modulate water permeability in the IMCD. The involvement of imidazoline receptors is inconclusive.

In a previous article labelled II a closed-form expression of the dynamic and static susceptibilities has been derived (J. Curely, Physica B 254 (1998) 277, previous article in this issue). In the present one, we mainly focus on the behaviours of the static susceptibility χ . In the low-temperature domain we point out the mechanisms involved in the construction of the 2D-spin arrangement; a very simple model allows one to give a good description of the χT behaviours. For a 2D-compensated antiferromagnet, we derive a linear variation between the temperature of the maximum of the susceptibility curve T ( χ max ) and the exchange energy J / k B . In addition, above the Neel temperature, there is a remarkable agreement between the experimental and theoretical susceptibilities, for the compounds BaMnF 4 and (CH 3 NH 3 ) 2 MnCl 4 . Finally, when T decreases from the high-temperature (HT) domain, we verify on these experimental results that the HT theoretical expansion of χ leads to a value lower than the one derived from Rushbrooke's HT series. In addition, it allows to fit all the experimental points belonging to the characteristic maximum of the susceptibility curve whereas the Pade method just permits to reach it before breaking down.

We discuss extensive sets of experimental data including static and dynamic light scattering, ultrasonic velocity measurements and high and low frequency dielectric relaxation, taken in the vicinity the critical point of a ternary microemulsion system. Upon approaching the critical point we observed a slowing down of the dielectric relaxation time and of the first cumulant of the time-dependent droplet density correlation function C2(t) which shows a non-exponential behavior at long time. These features can be well acccounted for by assuming that the microemulsion system is made of polydispersed transient fractal aggregates having a fractal dimension df=2.5 and a polydispersity index τ=2.2.

We discuss the static and dynamic critical behavior of binary solutions of water with some alkyl-oxyethylene-glycol monoether (CiEj) and of di 2 ethylhexyl sodium sulfosuccinate (AOT)-water-decane ternary microemulsion systems. Extensive sets of measurements of the scattered light intensity, of the order-parameter fluctuations time correlation function, and of the shear viscosity, have been performed for different systems. In most of the cases our data sets show systematic deviations from the behavior usually observed for molecular binary fluids. We show that generalized hydrodynamics cannot account for these deviations. A modified version of the Sorensen et al. (1976) dynamical droplet model has been worked out. This model which assumes that the physical clusters formed close to the critical point can be treated like percolating aggregates, and which includes the finite size of the monomers, very well accounts for all our experimental results.

We identified two cases of tuberculosis (TB) in office co-workers in Melbourne, Victoria, Australia; the Mycobacterium tuberculosis isolates were found to be identical with use of restriction fragment length polymorphism. Contact tracing was performed for 195 of 210 workers by means of the tuberculin skin test. Risk of infection was assessed according to a number of variables. Office contacts were exposed to infectious TB for 4 months; at least 24% of employees were infected. There was an association between sitting in proximity to the case during the period of exposure (OR, 4.24; 95% CI, 1.06-19.67). On-site workers had a higher risk of being infected (OR, 5.48; CI, 1.51-23.54) than did visiting workers. Workers in this office were exposed to open pulmonary TB for prolonged periods. The prevalence of TB infection (24%) among these workers was high compared with the infection rate (2%-7%) in the general community. Delay in diagnosis was the major factor responsible for the spread of TB in this office.

The three-component ionic microemulsion system consisting of AOT/water/ decane shows an interesting phase behavior in the vicinity of room temperature. The phase diagram in the temperature-volume fraction (of the dispersed phase) plane exhibits a lower consolute critical point at about 40°C and 8% volume fraction. A percolation line, starting from the vicinity of the critical point, cuts across the plane, extending to the high-volume fraction side at progressively lower temperatures. This phase behavior can be understood in terms of a system of polydispersed spherical water droplets, each coated by a monolayer of AOT, dispersed in a continuum of oil. These droplets interact with each other via a hard-core plus a short-range attractive interaction, the strength of which increases with temperature. We show that Baxter's sticky-sphere model can account quantitatively for the phase behavior, including the percolation line, provided that the stickiness parameter is a suitable function of temperature. We use the structure factors measured by small-angle neutron scattering below the critical temperature to determine this functional dependence. We also investigate the dynamics of droplets, below and approaching the critical and percolation points, by dynamic light scattering. Both theQ dependence of the first cumulant and the time evolution of the droplet density correlation function can be quantitatively calculated by assuming the existence of polydispersed fractal clusters formed by the microemulsion droplets due to attraction.

A theory for static and dynamic light scattering from micellar and microemulsion systems near the critical point is given which incorporates the universality of critical phenomena in fluids and the finite size effect of the constituent particles in the system. This theory reduces to the Ornstein-Zernike formula for the static light scattering intensity and the Kawasaki mode-coupling result for the line width of the dynamic light scattering in the limit when the size of the particles is vanishingly small compared to the wavelength of the probing light. When this is not the case the critical dynamics shows considerable deviation from the mode-coupling theory and the order parameter fluctuation exhibits non-exponential relaxation. The main ingredient of the theory is the recognition of the fact that the physical particle cluster size distribution near the critical point is nearly identical to the standard percolation cluster size distribution characterised by universal values of the fractal dimension D = 2.49 and of the polydispersity index τ = 2.21. We analysed light scattering data from several micellar solutions and a microemulsion system to support the validity of this theory and establish firmly that the underlying critical phenomena are indeed universal.

Experiments examined the effects of elevation of intracellular calcium concentration ([Ca2+]i) or activation of protein kinase C (PKC) on Na+ and water transport in the rat cortical collecting duct (CCD). We measured the lumen-to-bath 22Na+ flux (J1-->b), transepithelial voltage (VT), and water permeability (Pf) in CCD from deoxycorticosterone (DOC)-treated rats. Ionomycin (0.5 and 1 microM) and thapsigargin (1 and 2 microM) were used to increase [Ca2+]i. Phorbol 12-myristate 13-acetate (PMA; 0.3 and 1 microM) and oleoyl-acetyl-glycerol (OAG; 100 microM) were used as activators of PKC. [Ca2+]i was measured in isolated perfused tubules using the fluorescent dye fura 2. When added to the bathing solution, 220 pM arginine vasopressin (AVP) failed to affect [Ca2+]i, whereas 1 microM ionomycin increased [Ca2+]i by 103 +/- 15% and 2 microM thapsigargin increased [Ca2+]i by 24 +/- 4%. In flux studies, neither ionomycin nor thapsigargin affected J1-->b or Pf, although ionomycin caused marked morphological changes. Ionomycin also failed to alter either parameter in tubules from non-DOC-treated rats. Neither 100 microM OAG nor 1 microM PMA affected J1-->b or Pf. OAG at 50 microM had no effect on VT or transepithelial resistance, indicating no inhibition of conductive Na+ transport. We conclude that increased [Ca2+]i and PKC activation do not affect J1--b or Pf in the rat CCD. These findings may account for the sustained increase in J1--b produced in the rat CCD by AVP.

We report precise measurements of the time correlation function in a pseudo two-component water-in-oil microemulsion system made of surfactant AOT, water, and decane close to its consolute critical point and percolation threshold. Systematic studies of the intensity correlation functions using a correlator with a logarithmic sampling time show sizable deviations from a single exponential decay. It is shown that an extension of the dynamic droplet model is able to account for the nonexponential behavior at intermediate and long times. The linewidth is in satisfactory agreement with the model, which also takes into account the finite size of the microemulsion droplets

The three-component ionic microemulsion system consisting of AOT/water/decane shows an interesting phase behavior in the vicinity of room temperature. The phase diagram in the temperature-volume fraction (of the dispersed phase) plane exhibits a lower consolute critical point around 10% volume fraction and a percolation line, cutting across the plane starting from the vicinity of the critical point, extends to high volume fraction side, at progressively lower temperatures. This phase behavior can be understood in terms of a system of polydispersed spherical water droplets, each coated by a monolayer of AOT, dispersed in a continuum of oil. These droplets interact with each other via a hard-core plus a short-range attractive interaction, the strength of which increases with temperature. We show that Baxter's sticky sphere mode1 can account for the phase behavior including the percolation line, quantitatively, provided that the stickiness parameter is a suitable function of temperature. We use the structure factors measured by small angle neutron scattering below the critical temperature to determine this functional dependence. We also investigate the dynamics of droplets below and approaching the percolation line by dynamic light scattering. Both the first cumulant and the droplet density time correlation function can be quantitatively calculated by assuming the existence of polydispersed fractal clusters form by the microemulsion droplets due to the attraction. Analysis of SANS data indicates that above the percolation line, the clustered droplets structure gradually transforms into an ordered bicontinuous structure.

The reduction of methyl viologen (MV2+) and 9,10‐anthraquinone‐2‐sulfonate (AQS) by the benzopinacol anion in 50% (v/v) propan‐2‐ol/water was investigated spectroscopically. The rate constants for these reactions were found to be 12.9 ± 0.2 and 0.23 ± 0.01 M−1 s−1, respectively. © John Wiley & Sons, Inc. Copyright © 1992 John Wiley & Sons, Inc.

The reduction of methyl viologen (MV2+) and 9,10‐anthraquinone‐2‐sulfonate (AQS) by the benzopinacol anion in 50% (v/v) propan‐2‐ol/water was investigated spectroscopically. The rate constants for these reactions were found to be 12.9 ± 0.2 and 0.23 ± 0.01 M−1 s−1, respectively. © John Wiley & Sons, Inc. Copyright © 1992 John Wiley & Sons, Inc.

Fluoride flux in the rabbit CCD: A pH-dependent event. We measured fluoride flux (JF; pmol · min-1 · mm-1) in the isolated rabbit cortical collecting duct (CCD) to investigate the determining factors of JF. The perfusate contained 100 µM fluoride and the bath was fluoride-free. Osmotically-induced lumen-to-bath water flux did not affect JF. When perfusate pH was reduced from 7.4 to 6.1 and from 6.1 to 5.0, JF increased from 0.008 ± 0.002 to 0.027 ± 0.007 (P < 0.01) and from 0.018 ± 0.003 to 0.040 ± 0.005 (P < 0.01), respectively. Acetazolamide at 10-4M in the bath reduced JF slightly though not statistically. The anion-transport inhibitor, 4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid (DIDS), at 10-4M in the perfusate did not affect JF. Substitution of luminal chloride with gluconate failed to affect JF in tubules from normal rabbits or from rabbits treated with deoxycorticosterone which stimulates chloride-bicarbonate exchange in the CCD. JF showed no correlation with transepithelial voltage which ranged from +4 to -104 mV. We conclude that the luminal pH represents the primary determining factor influencing JF in the rabbit CCD, and fluoride does not use a chloride-mediated or a DIDS-inhibitory transport pathway.

The electrical conductivity of a three-component ionic microemulsion has been measured in the phase diagram region where the lamellar phase, made up of repeated layers of water, surfactant and oil, exists. The data have been analyzed on the basis of an effective medium theory expression, taking into account the ion distribution within the water layer according to the Poisson-Boltzmann equation. — PACS numbers: 64.60. Cn, 05.40. + j, 82.70. Dd

The authors have performed an extensive series of dynamic light scattering measurements of a three-component water-in-oil microemulsion system, consisting of AOT/water/decane, throughout the isotropic one-phase region at water to AOT molar ratio X=40.8, covering wide ranges of volume fraction phi and temperature T above and below the percolation threshold. The droplet density correlation function at long time has a nonexponential form for phi >0.4 and below the percolation threshold. When fitted to a stretched exponential function the apparent exponent beta , starting at about 0.7 at the lowest temperatures, increases continuously and approaches unity at the percolation temperature and above. The initial and the average decay rates of the correlation function, as a function of temperature, show an abrupt change of slope at the percolation threshold.

An extensive set of measurements of low-frequency conductivity \ensuremath{\sigma} of a three-component microemulsion system, sodium-di-2-ethyl-hexylsulfosuccinate (AOT)-water-decane, as a function of temperature (T from 10 to 50 \ifmmode^\circ\else\textdegree\fi{}C) and volume fraction of the dispersed phase (\ensuremath{\varphi} from 0.098 to 0.65) has been made. The measurements were made at a fixed value of the water-to-surfactant molar ratio equal to 40.8, where the microemulsion consists of AOT-coated water droplets, 85 \AA{} in radius, dispersed in oil. \ensuremath{\sigma} can be quantitatively calculated at low \ensuremath{\varphi} by means of a charge fluctuation model of Eicke et al., while it can be interpreted for higher vlaues of \ensuremath{\varphi} in terms of power-law behavior with indices related to the dynamic percolation picture below the threshold and the static one above it. The percolation locus in \ensuremath{\varphi}-T plane has been determined starting from the vicinity of the lower consolute point up to \ensuremath{\varphi}=0.65. This line can be successfully interpreted in terms of a modified version of the analytical theory of percolation given by Xu and Stell.

We report on a series of static and dynamic light-scattering experiments performed in a three-component water-in-oil microemulsion consisting of water/decane/AOT (sodium-di-2-ethyl hexyl sulfosuccinate). The measurements have been done throughout the isotropic one-phase region, in a large domain of volume fractions, as a function of temperature and scattering wave vector. For volume fractions φ > 0.42 the long-time tail of the droplet density correlation function S(Q t) is not an exponential, but tends toward a stretched exponential. The temperature and wave vector dependences of the first cumulant K1, and of the average relaxation time have bene investigated. These parameters change abruptly when crossing the well-defined electrical percolation locus. A theoretical model based on the aggregation of polydispersed fractal clusters of fractal dimension d=2, is in agreement with the experimental results.

The low-frequency electrical conductivity of water-in-oil microemulsions in presence of NaCl electrolyte solution has been measured in the temperature range from −15 to 60°C, for different volume fractions of the surfactant + water phase, in the interval from Φ = 0.1 to Φ = 0.8. The effects induced by the presence of the added salt, concerning the phase diagram in the (Φ − T) plane and the conductivity regimes far and close to the percolation, are discussed on the basis of the Eicke-Hall theory and a new approach to the conductometric behavior of microemulsions recently developed, which gives a more detailed and accurate description of the percolation characteristics.

The high-frequency dielectric relaxations of highly concentrated water-in-oil microemulsions have been investigated in the frequency range from 1 MHz to 1 GHz, at different temperatures, in the interval from 5 °C to 60 °C. In the region of the phase diagram studied, the system undergoes a progressive change of its structure, passing from water droplets dispersed in an oil matrix below percolation to two bicontinuous regions separated by a lamellar phase, above percolation. We have focused our attention on these two bicontinuous regions, where well-pronounced dielectric dispersions appear. An analysis in terms of scaling laws indicates a static percolation process above the percolation threshold and close to it and a process characterized by a very small value of the critical index, at higher temperatures, close to the phase transition.

10 pages, 2 tables, 6 figures., The formation of liposomes with low polydispersity index by application of ultrasounds was investigated considering methodology specifications such as sonication time and sonication power. Phosphatidylcholine (PC) liposomes were formed by the evaporation–hydration method. The vesicles were sonicated using several sonication conditions. The liposomes were then characterized by dynamic light scattering (DLS) and freeze-fracture electron microscopy (FFEM). Correlation functions from DLS were treated by cumulants method and GENDIST to obtain the mean radius and polydispersity index. These calculations allowed to fix an optimal sonication time (3000 s) and a useful interval of ultrasound power between 39 and 91 W. DLS and FFEM results confirmed that vesicle size, lamellarity and the polydispersity index decreased with the increase of sonication power. Thus, we propose a systematic method to form liposomes in which the physical characteristics of the vesicles may be controlled as a function of sonication time and power, The authors wish to thank the expert technical assistance of Dr. Carmen López Iglesias. This work was supported by funds from CICYT (MAT2001-1188-C02-02) and the financial support from the Grant FP-2001-1568

A new analytical concept is applied to the kinetics of the shrinking process of poly(N-isopropylacrylamide) (PNIPA) gels. When PNIPA gels are put into hot water above the critical temperature, two-step shrinking is observed and the secondary shrinking of gels is fitted well by a stretched exponential function. The exponent β characterizing the stretched exponential is always higher than one, although there are few analytical concepts for the stretched exponential function with β>1. As a new interpretation for this function, we propose a superposition of step (Heaviside) function and a new distribution function of characteristic time is deduced.

The properties of lamellar solutions formed in a quaternary mixture made of brine, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and glycerol have been studied under shear flow. As in AOT, brine pseudo-ternary system, the lamellar solutions exhibit a structural transition above a threshold shear rate, and form quasi-monodispersed multilamellar droplets. In this regime, the solutions are shear thinning. Both the viscosity and the droplet size scale with the shear rate with exponents respectively equal to -0.7 and -0.4. This last value is smaller than the one, 0.5, reported in the ternary systems. Tentative explanations of our experimental results are given.

Two separate cases of acute hepatitis C virus (HCV) infection following medical procedures, arthroscopy and colonoscopy, are reported. In both episodes, patient risk factors were reviewed, and staff and other patients' sera were tested for HCV antibodies and RNA. HCV RNA positive samples were genotyped, sequenced, and subjected to phylogenetic analysis. No risk factors for HCV infection were identified for either case except for medical procedures. HCV RNA positive patients were identified preceding both cases on the respective theatre lists. HCV infection in a second low risk patient was also identified. Nucleic acid sequencing and phylogenetic analysis of HCV from the two putative source patients and the three recipient patients demonstrated a high degree of relatedness respectively. The results suggest that patient-to-patient transmission occurred in both episodes via contamination of intravenous anaesthetic ampoules with HCV used on multiple patients. Injectable medication ampoules should not be used for more than one patient.

We investigate the effect of shear flow on a lamellar-sponge phase-separating fluid when subjected to shear flow. We show the existence of two different steady states (droplets and ribbons structures) whose nature does not depend on the way to reach the two-phase unstable region of the phase diagram (temperature quench or stirring). The transition between ribbons and droplets is shear thickening and its nature strongly depends on what dynamical variable is imposed. If the stress is fixed, flow visualization shows the existence of shear bands at the transition, characteristic of coexistence in the cell between ribbons and droplets. In this shear-banding region, the viscosity oscillates. When the shear rate is fixed, no shear bands are observed. Instead, the transition exhibits a hysteretic behavior leading to a structural bi-stability of the phase-separating fluid under flow.

The formation of closed-compact multilamellar vesicles (referred to in the literature as the "onion texture") obtained upon shearing lamellar phases is studied using small-angle light scattering and cross-polarized microscopy. By varying the shear rate gamma;, the gap cell D, and the smectic distance d, we show that: (i) the formation of this structure occurs homogeneously in the cell at a well-defined wave vector q(i), via a strain-controlled process, and (ii) the value of q(i) varies as (dgamma;/D)(1/3). These results strongly suggest that formation of multilamellar vesicles may be monitored by an undulation (buckling) instability of the membranes, as expected from theory.

18 pages, 9 figures, 3 tables.-- Printed version published Dec 1, 2003., Miniemulsions have been formed in quaternary systems water/hexanol/sodium dodecyl sulfate/decane by dilution of a microemulsion with an excess of water. We have investigated systematically the effect of composition variables in the droplet size and Ostwald Ripening rate. This droplet size has been investigated by using dynamic light scattering of samples submitted to further dilution in water. According to the dynamic light scattering results, the initial droplet size depends on the initial microemulsion water content, the larger the initial water concentration, the smaller the initial droplet size. This is probably related to the structure of the initial phase. The rate of Ostwald Ripening depends on the final surfactant concentration as expected for differences in interfacial tension. At high surfactant and dispersed phase contents, instability due to flocculation has been observed. Other experiments in which a fifth component (a more hydrophobic oil) was added to slow down Ostwald Ripening showed an initial droplet size increasing comparable to the systems without additive but after a relatively long time of approximately 2 h, a decrease was observed., Financial support from CIRIT (Generalitat de Catalunya) projects PIC 99-15 and ITT-CTP98-13 and MCYT MAT2001-1188-CO2-02.

We have studied by optical microscopy, small-angle light scattering, and rheology, the behavior under shear flow of a phase-separated lamellar-sponge (Lα − L3) ternary mixture. We observe in the Lα-rich region (ΦLα > 80%) the existence of a Newtonian assembly made of closed compact monodisperse lamellar droplets immersed in the sponge phase. Contrary to the classical onion glassy texture obtained upon shearing Lα phases, the droplet size scales herein as −1, the inverse of the shear rate. This result is in good agreement with Taylor's picture. Above a critical shear rate, c, the droplets organize to form a single colloidal crystal whose lattice size varies as −1/3. To the memory of Tess Melissa P.

We describe a new type of low-cost easy-to-use viscometer based on the temperature elevation in a liquid under shear flow. After calibration, this instrument can be used to measure the apparent steady state viscosity for both Newtonian and non-Newtonian liquids with no yield stress. We compute the rise in temperature due to viscous dissipation in a Couette cell and compare it to experimental results for different fluids. We show that the variation of the temperature with shear rate can be used to characterize the rheological behaviour of viscous fluids and to evaluate their viscosity in a large domain, from typically a few cP up to more than 10 P, with an accuracy of about ±5%. In contrast to simple viscometers, non-Newtonian fluids can be studied with this apparatus. We give experimental results for Newtonian and non-Newtonian liquids and show that they are very similar to those given in the literature by using much more sophisticated instruments.

We report on extensive measurements of the low and high frequencies sound velocity and sound absorption in AOT-water-decane microemulsions deduced from ultrasonic and, for the 7rst time as far as the absorption is concerned, from Brillouin scattering experiments. New experimental results on dielectric relaxation are also reported. Our results, which include data taken for critical as well as dense microemulsions, show new interesting relaxation phenomena. The relaxation frequencies deduced from very high frequency acoustical measurements are in good agreement with new high frequency dielectric relaxation measurements. We show that along the critical isochore, sound dispersion, relaxation frequency, and static dielectric permittivity can be accurately 7tted to power laws. The absolute values of the new exponents we derived from experimental data are nearly equal, and they are very close to � =0 :33 characterising the shape of the coexistence curve. The exponent characterising the in7nite frequency permittivity is very close to 0.04 relevant to the diverging shear viscosity. For dense microemulsions, two well de7ned relaxation domains have been identi7ed and the temperature variations of the sound absorption and the zero frequency dielectric permittivity bear striking similarities. We also show that the relaxation frequency of the slow relaxation process is almost independent of temperature and volume fraction and so cannot be attributed to percolation phenomena, whereas it can more likely be attributed to an intrinsic relaxation process probably connected to membrane

Dynamic light scattering experiments on lyotropic lamellar phases of brine and surfactant subjected to a flow field have been realized. The obtained results reveal that the relaxation times measured depend strongly on the velocity of the flow. This dependence is indicative of an increase of the effective elasticity modulus K and a decrease of the effective compressibility modulus (-)B of the lamellar phase with the flow velocity. This leads to the conclusion that the shear can induce a suppression of the undulation fluctuations of the bilayers of the lamellar phase. Our results show also that the rigidity of the membranes decreases as the salt concentration of the sample increases.

We report the effect of shear flow on a phase-separated system composed of lyotropic lamellar (L(alpha)) and sponge (L3) phases in a mixture of brine, surfactant, and cosurfactant. Optical microscopy, small-angle light, and x-ray scattering measurements are consistent with the existence of a steady state made of multilamellar ribbon-like structures aligned in the flow direction. At high shear rates, these ribbon-like structures become unstable and break up into monodisperse droplets resulting in a shear-thickening transition.

PGE2inhibits osmotic water permeability ( Pf) in the rat inner medullary collecting duct (IMCD) via cellular events occurring after the stimulation of cAMP, i.e., post-cAMP-dependent events. The α2-agonists also inhibit Pfin the rat IMCD via post-cAMP-dependent events. The purpose of this study was to determine whether PGE2plays a role in α2-mediated inhibition of Pf, Na+, and urea transport in the rat IMCD. Isolated terminal IMCDs from Wistar rats were perfused to measure, in separate experiments, Pf, lumen-to-bath22Na+transport ( Jlb), and urea permeability ( Pu). Transport was stimulated with 220 pM arginine vasopressin (AVP) or 0.1 mM 8-(4-chlorophenylthio)-cAMP (CPT-cAMP). Indomethacin was used to inhibit endogenous prostaglandin synthesis, and the α2-agonists clonidine, oxymetazoline, and dexmedetomidine were used to test the role of PGE2in the α2-mediated mechanism that inhibits transport. All agents were added to the bath. Indomethacin at 5 μM significantly elevated CPT-cAMP-stimulated Pf, Jlb, and Pu, and subsequent addition of 100 nM PGE2reduced these transport parameters. Indomethacin reversed α2inhibition of CPT-cAMP-stimulated Pf, Jlb, and Pu, and subsequent addition of PGE2reduced transport in each case. Indomethacin partially reversed α2inhibition of AVP-stimulated Pf, Jlb, and Pu, and PGE2reduced transport back to the α2-inhibited level. These results indicate that PGE2is a second messenger involved in the mechanism of transport inhibition mediated by α2-adrenoceptors via post-cAMP-dependent events in the rat IMCD.

We show the existence under shear flow of steady states in a two-phase region of a brine-surfactant system in which lyotropic dilute lamellar (non-Newtonian) and sponge (Newtonian) phases are coexisting. At high shear rates and low sponge phase-volume fractions, we report on the existence of a dynamic transition corresponding to the formation of a colloidal crystal of multilamellar vesicles (or "onions") immersed in the sponge matrix. As the sponge phase-volume fraction increases, this transition exhibits a hysteresis loop leading to a structural bistability of the two-phase flow. Contrary to single phase lamellar systems where it is always 100%, the onion volume fraction can be monitored continuously from 0 to 100 %.

Arginine vasopressin (AVP) increases water permeability in the collecting duct of the nephron via activation of adenylyl cyclase. Alpha-2 (alpha2) agonists inhibit AVP-stimulated water permeability via binding to alpha2 adrenoceptors that have been divided into 3 subtypes- alpha2A, alpha2B, and alpha2C. Some biological effects mediated by alpha2 agonists result from nonadrenergic imidazoline receptors that exist in the rat kidney. Thus, alpha2-inhibition of AVP-stimulated water permeability in the rat collecting duct could be caused by imidazoline receptors. The purpose of this study was to test agonists and antagonists selective for alpha2 and imidazoline receptors on AVP-stimulated water permeability in the rat inner medullary collecting duct (IMCD). Some experiments were conducted where water permeability was stimulated by a nonhydrolyzable analog of adenosine 3', 5'-cyclic monophosphate (cAMP). Agonists included dexmedetomidine, clonidine, oxymetazoline, agmatine and rilmenidine. The latter two are selective imidazoline agonists. Antagonists included yohimbine, RX821002, atipamezole, prazosin, WB4101, idazoxan, and BU239. Prazosin and WB4101 demonstrate selectivity for the alpha2B and alpha2C subtypes, respectively, and oxymetazoline and RX821002 are selective for the alpha2A subtype. BU239 is selective for imidazoline receptors. Wistar rat terminal IMCDs were isolated and perfused to determine the osmotic water permeability coefficient (Pf). All agonists except agmatine inhibited AVP-stimulated Pf. Inhibition by rilmenidine indicated a different mechanism of action from other agonists. Dose-response data show dexmedetomidine to be the most potent inhibitor. Oxymetazoline and clonidine inhibited cAMP-stimulated Pf indicating that the mechanism involves postcAMP cellular events. It was reported previously that dexmedetomidine inhibits cAMP-stimulated Pf (1). All antagonists except prazosin and WB4101 reversed alpha2-inhibition of AVP-stimulated Pf. BU239 was effective at 1 microM but not at 100 nM. Results suggest that alpha2A adrenoceptors modulate water permeability in the IMCD. The involvement of imidazoline receptors is inconclusive.

The aim of this study was to investigate effects on health of exposure to cyanobacteria as a result of recreational water activities. Participants, who were aged six years and over, were interviewed at water recreation sites in South Australia, New South Wales and Victoria on selected Sundays during January and February 1995. Telephone follow-up was conducted two and seven days later to record any subsequent diarrhoea, vomiting, flu-like symptoms, skin rashes, mouth ulcers, fevers and eye or ear irritations. On the Sundays of interview, water samples from the sites were collected for cyanobacterial cell counts and toxin analysis. There were 852 participants, of whom 75 did not have water contact on the day of interview and were considered unexposed. The 777 who had water contact were considered exposed. No significant differences in overall symptoms were found between the unexposed and exposed after two days. At seven days, there was a significant trend to increasing symptom occurrence with duration of exposure (P = 0.03). There was a significant trend to increasing symptom occurrence with increase in cell count (P = 0.04). Participants exposed to more than 5000 cells per mL for more than one hour had a significantly higher symptom occurrence rate than the unexposed. Symptoms were not correlated with the presence of hepatotoxins. These results suggest symptom occurrence was associated with duration of contact with water containing cyanobacteria, and with cyanobacterial cell density. The findings suggest that the current safety threshold for exposure of 20,000 cells per mL may be too high.