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African elephants face an uncertain future. Politics, war, sustained media campaigns, corrupt, weak or absent institutions supporting conservation, land-use planning or general governance, and greed are all bringing elephants into direct conflict with humans. Although elephant populations have declined considerably relative to their historical size and range, human populations have expanded to occupy and intensively use remaining elephant areas. Strategies to minimize perceptions of conflict and the implementation of land-use planning with biodiversity protection as its goal could help to sustain at least some populations of elephants. Here, we review threats to elephants, with an emphasis on those resulting from human perceptions of conflict, and suggest some mechanisms for grappling with these threats.

The conformation and dynamics of a single DNA molecule undergoing oscillatory pressure-driven flow in microfluidic channels are studied using Brownian dynamics simulations, accounting for hydrodynamic interactions between segments in the bulk and between the chain and the walls. Oscillatory flow provides a scenario under which the polymers may remain in the channel for an indefinite amount of time as they are stretched and migrate away from the channel walls. We show that by controlling the chain length, flow rate, and oscillatory flow frequency we are able to manipulate the chain extension and the chain migration from the channel walls. The chain stretch and the chain depletion layer thickness near the wall are found to increase as the Weissenberg number increases and as the oscillatory frequency decreases.

We report quantitative measurements of Marangoni flows generated at the surfaces of aqueous solutions by using water-soluble redox-active surfactants in combination with electrochemical methods. These measurements are interpreted within the framework of a simple model that is based on lubrication theory and the proposition that the kinetics of the desorption of redox-active surfactants from the surfaces of aqueous solutions plays a central role in determining the strength of the Marangoni flow. The model predicts that the leading edge velocity of the Marangoni flow will decay exponentially with time and that the rate constant for the decay of the velocity can yield an estimate of the surfactant desorption rate constant. Good agreement between theory and experiments was found. By interpreting experimental measurements of electrochemically generated Marangoni flows within the framework of the model, we conclude that the desorption rate constant of the redox-active surfactant Fc(CH2)11−N⁺(CH3)3Br^-, where Fc is ferrocene, is 0.07 s^-1. We also conclude that the ionic strength of the aqueous solution has little effect on the desorption rate constant of the ferrocenyl surfactant.

Simulations were conducted to elucidate the effects of Marangoni convection on the cyclic voltammograms of Langmuir films of redox-active amphiphiles. Oxidation and reduction of the amphiphiles occur at a line electrode that contacts the Langmuir film, and oxidation is assumed to introduce an electrostatic contribution to the surface equation of state of the film. A boundary element method is used to compute the bulk fluid velocities that are induced by the corresponding surface tension gradients and a finite element method used to compute the surface transport of the surfactants. When compared with the case of purely diffusional transport processes, the simulation results reveal that when Marangoni convection is included, the cyclic voltammograms become asymmetric. The anodic peaks tend to be larger and sharper than the cathodic and the ratio of cathodic peak to anodic peak is about 0.808. The results of the simulation are compared to past reports of cyclic voltammograms of Langmuir monolayers of a ferrocenyl amphiphile, and good agreement is found.

The constrained recovery of polymeric fluids following cessation of steady shear flow is studied using linear bead−spring chain models for dilute polymer solutions and the Curtiss−Bird model for polymer melts. Brownian dynamics simulation techniques are combined with a spectral method for solution of the continuum equation of motion. The shear stress required to solve the continuum equation is computed directly from ensemble averages over internal configurations of model molecules, thereby eliminating the need for a closed-form constitutive equation. Simultaneous solution of the equation of motion for actual fluid velocities obviates the linear velocity profile assumption used in previous studies of constrained recoil. For each of the models examined in the present work, a maximum was observed in the overall recovery with increasing steady-state shear rate. These maxima are an inherent consequence of the polymer models' shear thinning behavior but are more pronounced if the assumption of a linear velocity profile is relaxed.

Abstract: Various microstructural pictures for slip at polymer/solid interfaces lead to relations which have a region where multiple values of slip velocity are predicted for the same shear stress. This leads to the expectation of multivalued flow curves, which has been verified in specific cases by numerous researchers. We study the effect of pressure dependence on flow curve multiplicity using a simple multivalued slip relation to model the phenomena of hysteresis and spurt flow in polymer extrusion. A continuation technique is used to trace out the boundaries of the region of flow curve multiplicity as pressure drop and die length to diameter (L/D) ratio are changed. Results for Newtonian, shear thinning and viscoelastic constitutive equations show that, despite the multivalued nature of the slip model, multiplicity (and thus hysteresis) is absent at high L/D.  For the sake of completeness, we also carry out time-dependent simulations at constant piston speed taking fluid compressibility into account. These simulations show that oscillations in the pressure drop and exit volumetric flow rate result only if the system is operated in the multiplicity region of the steady state flow curve, in agreement with the results of similar simulations by researchers using various multivalued slip models without pressure dependence. The results demonstrate that a multivalued slip model does not guarantee multiplicity in the flow curve for the constant pressure drop operation, nor oscillations for constant piston speed operation.

Viscoelastic flow instabilities can arise from gradients in elastic stresses in flows with curved streamlines. Circular Couette flow displays the prototypical instability of this type, when the azimuthal Weissenberg number Weθ is O(ε−1/2), where ε measures the streamline curvature. We consider here the effect of superimposed steady axial Couette or Poiseuille flow on this instability. For inertialess flow of an upper-convected Maxwell or Oldroyd-B fluid in the narrow gap limit (ε≪1), the analysis predicts that the addition of a relatively weak steady axial Couette flow (axial Weissenberg number Wez=O(1)) can delay the onset of instability until Weθ is significantly higher than without axial flow. Weakly nonlinear analysis shows that these bifurcations are subcritical. The numerical results are consistent with a scaling analysis for Wez≫1, which shows that the critical azimuthal Weissenberg number for instability increases linearly with Wez. Non-axisymmetric disturbances are very strongly suppressed, becoming unstable only when ε1/2Weθ= O(We2z). A similar, but smaller, stabilizing effect occurs if steady axial Poiseuille flow is added. In this case, however, the bifurcations are converted from subcritical to supercritical as Wez increases. The observed stabilization is due to the axial stresses introduced by the axial flow, which overshadow the destabilizing hoop stress. If only a weak (Wez1) steady axial flow is added, the flow is actually slightly destabilized. The analysis also elucidates new aspects of the stability problems for plane shear flows, including the exact structure of the modes in the continuous spectrum, and illustrates the connection between these problems and the viscoelastic circular Couette flow.

The clinical problem of bacterial identification has been approached by applying pattern-recognition techniques to multi-wavelength surface-scattering and reflectance data derived from real-time scans of isolated colonies. Preliminary results, obtained from blood-agar plates inoculated with a mixture of staphylococci, streptococci and escherichieae, indicate that these organisms can be differentiated with better than 90% certainty, provided the colonies are physically separated and their growth conditions closely controlled. Data collection and classification characteristics of the experimental system are briefly described; it is felt that the technique, possibly expanded to include boundary characteristics of the colonies, may offer a viable means of identifying clinically important bacteria.

— The relationship between the malleus handle and the tympanic membrane in humans has been studied with primary attention being directed to the fibrous layer of the tympanic membrane and its method of attachment to the malleus. This attachment is most intimate at the level of the umbo and becomes progressively more tenuous as the short process is approached. The long process of the malleus, comprised of a bony core, has a definite sleeve of cartilage surrounding its entire length. This cartilage is surrounded by a perichondrial layer which has previously been termed a periosteum. In the lower third, the fibrous lamina propria appears to split equally and the fibers then blend imperceptively with those of the perichondrial layer surrounding the manubrium. At high levels, the attachment is less intimate, most of the fibers appearing to pass lateral to the malleus handle. The embryologic development of the tympanic membrane-malleus junction has been considered and the anatomical features of this area have been considered in relation to functional requirements.

DISCUSSION Shannel TMnmel ~~~~~~a~~ J. P Taberner, R. Napthine, D. J. Steer, R. Smart, K R.Kershaw, A. G. McCulloch, M. Gladstone, J. G. Grant, A. J. Powderham, D. K. Young, J. C. Duggleby, J. E C. Pilkington and T McGuirk Dr T. K. Chaplin, Fellow Compensation in the UK for compulsory purchase was apparently based on very conservative valuation,paid very late...

Background. The volatile anaesthetics isoflurane and sevoflurane induce both negative and positive inotropic effects in ventricular myocytes, the mechanisms of which are not fully understood. Previous data suggest that changes in myofilament Ca2+ sensitivity contribute to their sustained negative inotropic effects. In this study, the role of changes in myofilament Ca2+ sensitivity in both positive and negative inotropic effects of these agents was examined in intact ventricular myocytes. Methods. Contractility and cytosolic Ca2+ (fura-2) were recorded optically in ventricular myocytes stimulated electrically (1 Hz) at 30°C. Myofilament Ca2+ sensitivity was assessed from plots of cell length against fura-2 fluorescence ratio (Fr) from individual twitches at various points before, during and after a 1 or 4 min exposure to 0.6 mM anaesthetic. Results. Isoflurane reduced mean (sd) myofilament Ca2+ sensitivity from 10.3 (1.9) to 5.9 (1.6) µm Fr−1 (P<0.001) throughout a 1 min exposure, which returned to control on removal. In contrast, on initial exposure to sevoflurane, Ca2+ sensitivity was reduced from 10.8 (1.3) to 4.3 (0.9) µm Fr−1 (P<0.001) but this recovered partially towards control over 3 min. On removal, sensitivity was increased above control (to 17.7 (2.2) µm Fr−1; P<0.001) before preanaesthetic levels were restored. Conclusions. These data show that both isoflurane and sevoflurane reduce apparent myofilament Ca2+ sensitivity at steady state. However, sevoflurane (but not isoflurane) induced transient changes in apparent myofilament Ca2+ sensitivity, which would contribute to its inotropic profile.