Absence Of Wind Research Articles

Pharmaceutical and medical applications of polymer electrolytes

Classic methods of drug delivery have embraced a number of routes into the site of pharmacological action. Modern preference, wherever possible, is for a non-invasive route to minimise the chance of cross infection, especially of the AIDS virus. The skin, which is the largest organ in the human body, is a particularly appealing route as, in the absence of wounds and blemishes, it offers a natural, high-integrity, barrier to the outside world. Skin patches containing active drug that is allowed to diffuse passively across the external skin barrier into the bloodstream now enjoy wide application but a problem is that the rate of egress is often slow. For certain ionic drugs, including local anaesthetics and, more recently, peptides and gene-based, biotechnological engineered pharmaceuticals, it is possible substantially to enhance transdermal transport by iontophoresis. The technique of iontophoresis facilitates the passage of ionic drugs through the skin using an electric current. Ionically conducting polymers (polymer electrolytes) are potential candidates as hosts for drugs to be delivered iontophoretically. Key issues affecting iontophoretic delivery are reviewed in this paper and the potential role of polymer electrolyte materials in iontophoretic devices will be described.

Langmuir circulations beneath growing or decaying surface waves

The instability to longitudinal vortices of two-dimensional density-stratified temporally evolving wavy shear flow is considered. The problem is posited in the context of Langmuir circulations, LCs, beneath wind-driven surface waves and the instability mechanism is generalized Craik–Leibovich, either CLg or CL2. Of interest is the influence of non-stationary base flows on the instability according to linear theory. It is found that the instability is described by a family of similarity solutions and that the growth rate of the instability, in non-stationary base flows, is doubly exponential in time, although the growth rate reduces to exponential when the base flow is stationary. An example is given for weakly sheared wind-driven flow evolving in the presence of growing irrotational surface waves. Waves aligned both with the wind and counter to it are considered, as is the role of stratification. Antecedent to the example is an initial value problem posed by Leibovich & Paolucci (1981) for neutral waves in slowly evolving shear. Here, however, the waves and shear may grow (or decay) at rates comparable with the LCs. Furthermore the current here has two components: a wind-driven portion due to the wind stress applied at the free surface and a second due to the diffusion of momentum due to the wave-amplitude-squared free-surface stress condition. Using the case for neutral waves in non-stratified uniform shear for reference, it is found, in general, that growing waves are stabilizing while decaying waves are destabilizing to the formation of LCs, although the latter applies only for sufficiently large spanwise spacings and is subject to a globally stable lower bound. Decaying waves in the absence of wind can also be destabilizing to LCs. When the wind is counter to the waves, however, only decaying waves are unstable to LCs. Furthermore, while growing waves are stable to the formation of LCs in the presence of stable stratification, decaying waves are unstable in both aligned and opposed wind-wave conditions. Unstable stratification on the other hand, is destabilizing to LCs for all temporal waves in both aligned and opposed wind-wave conditions.

Oceanic inflow from the Coral Sea into the Great Barrier Reef

Long-term current meter data from the continental shelf region of the Great Barrier Reef show that there exists a zone of oceanic inflow onto the shelf. This oceanic inflow splits into two branches on meeting the continental shelf slope, resulting in two net longshore currents on the slope, one to the north and the other to the south of the separation point. In 1981 this separation point was located between 17°S and 18°S. This circulation was successfully predicted using a depth-averaged two-dimensional model in which the regional sea level gradient is explicitly added in the momentum equations. The resulting circulation on the continental shelf is controlled by an oceanic inflow of 0·58Sv, spread over 500km of the shelf edge both north and south of the separation point. The inflow appears measurably impeded by the presence of coral reefs, with >50% of the inflow occurring in a 150km long area where reef density is small. Satellite images confirm this spatial variability. Longshore currents on the shelf generated by the inflow are modulated by the wind and tides, which can deflect the mean current away from areas of high reef density and generate localized outflows to the Coral Sea. Oceanic inflow is believed to be important because it flushes the shelf even in the absence of wind; it controls the dominant direction of across-shelf and along-shelf spread of spawn material from reefs; it makes it possible for upwelled water to spread quickly over the GBR shelf; it may also protect coral reefs by preventing river plumes from spreading onto the outer shelf.

Penetration of Picea sitchensis root bark by Armillaria mellea, Armillaria ostoyae and Heterobasidion annosum

Penetration of root bark tissues of Picea sitchensis by Armillaria ostoyae, Armillaria mellea and Heterobasidion annosum was examined in the absence of wounds, in superficial wounds (rhytidome tissues removed to expose the secondary phloem) and in wounds to the depth of the vascular cambium (deep wounding). Both species of Armillaria penetrated bark without prior wounding, but neither species formed rhizomorphs in this treatment. Armillaria ostoyae penetrated to 39 cell layers in depth by 48 days after inoculation of unwounded bark, whereas A. mellea penetrated 25 cell layers in the same time. Armillaria mellea penetrated superficial wounds significantly more rapidly than did A. ostoyae. Both species produced rhizomorphs within wounded host tissues. Inoculation of deep wounds with Armillaria resulted in a greater depth of bark necrosis with A. mellea than with A. ostoyae. In the absence of wounding, H. annosum failed to penetrate root bark tissues, but in both superficial and deep wounds hyphae penetrated beyond the ligno–suberized boundary zone (LSZ) by 12 days after inoculation. Where no inoculations were made, superficial or deep wounding led within 25 days to the restoration of a structurally continuous LSZ, and by day 48 the wound periderm (WP) was fully differentiated. In inoculated wounds, however, formation of the LSZ and WP was delayed or inhibited in most trees, particularly following inoculation with A. ostoyae or A. mellea. Suberization in the LSZ and WP remained diffuse and discontinuous 48 days after inoculation. Moreover, the presence of WP did not prevent further penetration of the tissues by the pathogens. Variations between trees in the depth of pathogen penetration were noted, possibly indicating differing susceptibilities of individual host genotypes. The possible host factors involved in resistance to penetration of root bark tissues by Armillaria and Heterobasidion are discussed.

Mechanisms of low‐grazing‐angle scattering from spilling breaker water waves

The low‐grazing‐angle electromagnetic scattering from spilling breaker water waves has been examined using a numerical approach. A moment‐method‐based electromagnetic technique was used to find the instantaneous scattering from the crests of breakers generated mechanically in a wave tank in the absence of wind. A high‐speed imaging system carried on an instrument carriage traveling at the phase velocity of the breakers provided continuous measurements of the temporal evolution of the crest shape, in turn allowing a continuous calculation of the microwave backscatter from the crest. As the wave steepens and a bulge forms on the forward face of the crest, horizontal‐to‐vertical polarization backscattering ratios (HH/VV) as high as 0 dB are observed. Greatly reduced ratios are observed after breaking when no steep features remain on the wave. A time‐dependent Fourier analysis identifies “fast” scattering whose Doppler shifts are nearly equal to or greater than the phase velocity of the breaker, and “slow” scattering whose Doppler shifts are consistent with the orbital motion of the breaker. Comparison of the Doppler shifts with the measured wave profiles shows that the fast scattering identified is associated with very steep surface features that give specular (or nearly specular) reflection points on the surface, but the magnitude and HH/VV ratio of the response to a specific steep feature depends upon its electromagnetic size, thus giving a frequency dependence. The slow scattering identified (in the absence of wind) is correlated with the “turbulent scar” that remains after breaking.

Compensatory Responses in Growth and Fecundity Traits of Sinapis alba L. Following Release from Wind and Density Stress

Plant responses to short‐term stress are usually extrapolated to long‐term effects, neglecting examination of the capacity of plants to compensate for stress. We examined the capacity of Sinapis alba plants to compensate for wind and density stress through responses in growth and fecundity traits. Plants were grown under three wind speeds and two densities for three periods (11, 17, or 24 d). During these periods, there were significant losses in growth, thus confirming that plants were stressed. The plants were then allowed to recover in the absence of wind and at reduced density. Following this recovery, measurements of growth, allocation, and reproductive parts were taken. Biomass had been regained in wind‐stressed plants relative to control plants, and reproductive attributes were no different, except that flowering time was delayed until 4 d with increased wind. Plants compensated less effectively for density stress with respect to growth and reproduction, but root:shoot allocation was greater in the control plants. Plants were unable to fully compensate for the longest exposure times. We conclude that the effects of short‐term stress cannot be extrapolated to long‐term effects and that under favorable environmental conditions, the compensatory capacity of Sinapis depends on the severity and duration of the stress.

Cycling on Earth, in space, on the Moon.

The mechanical power for cycling (P(c)) at constant ground speed (s), in the absence of wind on smooth hard terrain is the sum of the power dissipated against rolling resistance, gravity and air resistance: P(c)=a x s + M x g x s x sin gamma + b x S3, where a and b are constants, M is the mass of the subject plus bike, g is the acceleration of gravity and gamma is the angle of the terrain with the horizontal. The constant b depends upon the drag coefficient (Cd), the overall area projected on the frontal plane (A(f)), and the air density (rhoa): b = 0.5 x C(d) x A(f) x rhoa. In turn, rhoa depends on air pressure (P(B)) and temperature (T): rhoa=rho0 x 0.359 x P(B) x T(-1), where rho0 is the air density at 760 mmHg (101.3 kPa) and 273 K. The metabolic power developed by the cyclist (E(c)) is related to P(c) E(c) = P(c) x eta(-1), where eta is the mechanical efficiency of cycling. The experimental values of a, b and eta are fairly well known so that, if the maximal metabolic power as a function of the performance time is known for a given cyclist, the following set of data can be individually calculated: (1) best performances over any given distance and for any given altitude above sea level, (2) the effects of posture and body size on maximal speeds, and (3) the maximal incline of the terrain that can be overcome at any given speed or coasting speed for any given downslope. The above set of information makes it possible also to calculate the characteristics of a "Twin Bikes System" (TBS) for preventing microgravity deconditioning during long-term space flight. The TBS consists of two bicycles that are mechanically coupled by a differential gearing, which move at the very same speed, but in the opposite sense, along the inner wall of a cylindrically shaped space module. The circular trajectories induce a centrifugal acceleration vector (a(c)) oriented along the head-to-feet direction of each subject: a(c) = v(t)2 x r(-1) where v(t) is the tangential velocity and r the radius of gyration, which is equal to the inner radius of the space module. So, any desired value of a(c) can be achieved by appropriately selecting v(t), wherefrom the mechanical and metabolic powers that the astronauts must generate can be readily calculated. Experiments performed in a ground-based human centrifuge have shown that the discomfort derived from the rotating environment is reasonably low and well tolerated. If the appropriate atmospheric pressure is provided, cycling on circular or elliptical tracks may be useful to reduce cardiovascular deconditioning that occurs due to the reduced gravity in permanently manned lunar bases. Indeed, on the curved parts of the path a cyclist will generate a horizontal outward acceleration: a(c) = s2 x r(-1), where s is the velocity along the track and r is the radius of curvature. To counterbalance a(c), the subject plus bike must lean inwards so that the vectorial sum of a(c) plus the lunar gravity (g(L) = 1.62 m x s(-2)) is applied along a straight line that includes the centre of mass of the system and the point of wheel contact with the ground. For values of s from 10 to 20 m x s(-1) and r from 50 to 200 m, this vectorial sum ranges from 1.05 to 5.03 g(L) (0.17-0.83 g).

On the absence of winds in advection-dominated accretion flows

ABSTRA C T We show that recently published assertions that advection-dominated accretion flows (ADAFs) require the presence of strong winds are unfounded because they assume that low radiative efficiency in flows accreting at low rates on to black holes implies vanishing radial energy and angular momentum fluxes through the flow (which is also formulated in terms of the ‘Bernoulli function’ being positive). This, however, is a property only of self-similar solutions which are an inadequate representation of global accretion flows. We recall general properties of accretion flows on to black holes and show that such, necessarily transonic, flows may have either d positive or negative Bernoulli function depending on the flow viscosity. Flows with low viscosities Oa & 0:1 in the a-viscosity model) have a negative Bernoulli function. Without exception, all 2D and 1D numerical models of low-viscosity flows constructed to date experience no significant outflows. At high viscosities the presence of outflows depends on the assumed viscosity, on the equation of state and on the outer boundary condition. The positive sign of the Bernoulli function invoked in this context is irrelevant to the presence of outflows. As an illustration, we recall 2D numerical models with moderate viscosity that have positive values of the Bernoulli function and experience no outflows. ADAFs, therefore, do not differ from this point of view from thin Keplerian discs: they may have, but they do not have to have, strong winds.

Flight energetics and dispersal capability of the fire ant, Solenopsis invicta Buren

Experiments were conducted to estimate the flight capabilities of fire ant (Solenopsis invicta Buren) alates. These experiments were designed to: (1) quantify energetic expenditure during fixed flight; (2) characterize metabolic substrates of male and female alates; (3) estimate flight speed of male and female alates; and (4) quantify wingbeat frequency and water loss of females during flight. Flying males (in closed-system respirometry) increased metabolic rate approximately 38.4-fold over resting rate. Females increased metabolic rate approximately 51-fold (closed-system respirometry) and 48-fold (flow-through respirometry) over resting rate. Female alates had a mean respiratory quotient (RQ) of 0.999, indicating reliance on carbohydrates. The mean RQ of males was significantly lower (0.867). The flight speed of females on a circular flight mill averaged approximately 0.7 m s−1, and increased with temperature but decreased with increasing body mass. The flight speed of males was 43% greater (approximately 1.0 m s−1) and increased linearly with temperature and increasing body mass. Female alates lost an average of 1.8 mg water h−1 during flight. A simple energetics model, combined with previous work on the nutrient content of S. invicta and patterns of CO2 release observed in this study, indicate that the flight capability of S. invicta female alates is limited to <5 km in the absence of wind.

Convective water exchanges in a wind-sheltered littoral region of Eau Galle Reservoir, Wisconsin USA

Rates of convective water exchange were estimated for periods of differential cooling from a heat budget model, based on detailed changes in water temperature at stations positioned along the littoral slope of the macrophyte-occupied southwest embayment in Eau Galle Reservoir, Wisconsin. Differential cooling and convective water exchanges occurred nightly over a study period of 14 days in August, 1991. Although wind speeds were negligible during most of the nights, estimated rates of convective exchange (grand mean = 0.00066 m 3 m -1 s -1 ) were sufficient to result in a residence time of only ∼1 day in this embayment. Rates of convective exchange calculated via a heat budget model in 1991 were very similar in magnitude to rates measured in 1989 in another embayment of Eau Galle Reservoir using dye as a tracer for water movement. Our results suggest that substantial horizontal water movements and solute transport can occur in the absence of wind in vegetated littoral regions of lakes.

CARACTERIZAÇÃO HIDRÁULICA DO MICROASPERSOR RAIN-BIRD QN-14

RESUMO Este trabalho foi realizado no Centro de Pesquisa Agropecuária do Trópico Semi-Árido (Embrapa Semi-Árido) com o objetivo de se obter as características hidráulicas do microaspersor Rain bird QN-14. O coeficiente de variação de fabricação (CVF) foi de 0,7%, que, de acordo com a ABNT, é considerado bom. A equação característica, Q = 45,63H0'4866, foi ajustada através de regressão linear, com um coeficiente de determinação (r2)de 0,9998. O emissor apresentou intensidade de precipitação média de 1,64 mm h-1 ao longo do raio; a intensidade de precipitação até 1,00 m do emissor foi inferior a 10% da média, ficando seu raio efetivo limitado entre 1,00 e 3,00 m de distância, enquanto o coeficiente de uniformidade de Christiansen, na ausência de vento, foi da ordem 15,43% sem, contudo, levar em consideração seu raio efetivo.

Lineshape analysis of breaking-wave Doppler spectra

Based on analyses of spectral densities of microwave backscatter from ocean waves, it has previously been observed that the Doppler spectra could be decomposed into different components, with Bragg scatterers represented by Gaussian lineshapes and faster-than-Bragg scatterers represented by Lorentzian and/or Voigtian lineshapes. It has been conjectured that the faster-than-Bragg scatterers are due to scattering from breaking waves, and established that the scattering mechanisms are non-Bragg in nature. In order to test the conjecture regarding the decomposition of spectral lineshapes which represent meaningful scattering processes, experiments have now been conducted at a wave tank facility. The lineshapes of breaking-wave Doppler spectra are analysed. It is found that for mechanically-generated breaking waves in the absence of wind, the co-polarised (HH and VV) spectra have predominantly Voigtian or Lorentzian shape and that the cross-polarised (VH and HV) spectra have exclusively Voigtian shape.

Scattering from breaking gravity waves without wind

Scattering experiments from breaking gravity waves conducted at a wave tank facility at small grazing angles in the absence of wind are analyzed. Breaking gravity waves are studied using a fully plane polarimetric horizontal (HH), vertical (VV), vertically transmitted and horizontally received polarization (VH), and horizontally transmitted and vertically received polarization (HV) pulse-chirped X-band (8.5-9.6 GHz) radar in conjunction with optical instruments: the plane polarimetric optical specular event detector (OSED) and side-looking camera (SLC). Spatially and temporally resolved radar backscatter has been measured and temporally correlated to the data obtained from the optical diagnostics. The experiments yield the following results: (1) enhanced scattering compared to Bragg scattering levels occurs throughout the evolutionary process of wave-breaking, i.e., the radar scatters strongly from both the unbroken and broken surfaces; (2) an explanation is found for the observation that the scatterer Doppler frequency is slightly less than the Doppler frequency corresponding to the fundamental wave phase speed; (3) a representative non-Bragg cross section of a breaking wave can be obtained; and (4) a breaking wave surface is found to be an efficient depolarizer.

Doppler radar backscatter from ring waves

The effects of rain falling on the sea surface have been investigated using a 3 GHz Doppler radar. In the absence of wind, the field measurements of radar backscatter show an enhancement of surface roughness due to a 4 mm hr 1 rainfall, which is equivalent to a light wind of several m s 1, but without the azimuthal variation characteristic of wind generated roughness. The radar Doppler spectra are dominated by dual peaks corresponding to scatterers both approaching and receding from the radar at the phase velocity of the resonant Bragg wave. This indicates that the dominant backscatter mechanism from this rain-roughened sea was resonant Bragg scatter from ring-waves expanding outward from the sites of droplet impacts. A secondary feature of the Doppler spectra which may be backscatter from stalks, is characterized by intermittent, weaker returns at velocities that are approximately stationary relative to the water surface. The Doppler spectral widths indicate that ring-wave lifetimes exceed 300ms.

Modelling of the propagation and transformation of riverine waters over the north-western shelf and in the abyssal part of the Black Sea

To study the propagation and transformation of riverine waters in the framework of a multilayer model based on primitive equations, the method of through counting is suggested, involving two types of grids, namely, a fine grid in the north-western shelf area and a large-sized grid in the deep sea. It has been shown that, in the absence of wind, riverine waters propagate over the shelf and along the western coast of the sea. North-easterly wind presses this flow against the shore, thus intensifying it; as a result of this, brackish waters turn out to be nearly entirely driven from the north-western shelf area and concentrate in the western section of the open sea where they form a layer that is quasi-homogeneous, in terms of salinity. Due to the forcing of the north-westerly wind, riverine waters penetrate into the interior of the shelf area and then move southward toward the open sea, mixing up with the upwelling abyssal saltier waters and forming a tongue of relatively brackish waters in the central part of the western half-basin.

Diffusive escape in a nonlinear shear flow: Life and death at the edge of a windy cliff

The survival probability of a particle diffusing in the two dimensional domain $x>0$ near a ``windy cliff'' at $x=0$ is investigated. The particle dies upon reaching the edge of the cliff. In addition to diffusion, the particle is influenced by a steady ``wind shear'' with velocity $\vec v(x,y)=v\,{\rm sign}(y)\,\hat x$, \ie, no average bias either toward or away from the cliff. For this semi-infinite system, the particle survival probability decays with time as $t^{-1/4}$, compared to $t^{-1/2}$ in the absence of wind. Scaling descriptions are developed to elucidate this behavior, as well as the survival probability within a semi-infinite strip of finite width $|y|<w$ with particle absorption at $x=0$. The behavior in the strip geometry can be described in terms of Taylor diffusion, an approach which accounts for the crossover to the $t^{-1/4}$ decay when the width of the strip diverges. Supporting numerical simulations of our analytical results are presented.

Unsteady heat-transfer effects on the spreading and dilution of dense cold clouds

The transient heating effects on cold clouds spreading, in the absence of wind, over much warmer ground surfaces, are examined. The heat flux from the ground to the cloud affects both the rate of spreading and the cloud longevity. The effects are most pronounced for surfaces that are good conductors, but substantial corrections are found for cryogenic releases on all surfaces of practical interest. The theoretical results are applicable also to hot-fire plumes spreading under a cold ceiling. They have been verified by comparison with existing experiments in channels, i.e. a heavy-gas (cryogenic) ground release as well as a hot-fire plume under the ceiling. A simple analytic solution is also given, which shows explicitly the role of various (dimensionless) parameters. This simplified solution shows good agreement with both the exact numerical solution and the experiments and it requires only algebraic evaluation.

Dynamic properties of orientation to turbulent air current by walking carrion beetles

A beetle orients its walk with respect to the direction of even a brief air current lasting only a few seconds. In a discontinuous current, the degree of orientation increases with the proportion of time during which the air flows. In the absence of wind, a walking beetle generates its own opposing airstream, the velocity of which is rhythmically modulated. Sinusoidal modulation of the wind direction elicits approximately sinusoidal changes in walking direction. The amplitude of the following response at frequencies below 0.1 s-1 is almost as large as the amplitude of the change in wind direction. As the stimulus frequency increases, the response amplitude decreases. The Bode plot shows that at frequencies above 1 s-1 the phase of the following response lags by almost 360 &deg;. The dynamic temporal behaviour of the wind-orientation system is comparable with that of a control mechanism having low-pass characteristics of at least second order. It follows that rapid changes in wind direction do not immediately affect orientation behaviour. The wind-orientation system is thus well adapted to the air currents recorded in nature which, at the level of a walking beetle, can change very quickly and erratically in both direction and velocity.

DESIGN OPTIMIZATION OF AN ELECTROSTATIC MICROMOTOR WITH AXIAL FIELD

Historically, the idea of using electrostatic phenomena to produce motion has long stimulated the activity of scientists. Although the power generated by electrostatic motors is modest, the absence of windings and ferromagnetic material makes this kind of device competitive for applications characterized by low levels of torque and reduced volumes. During last years a renewed attention appeared towards electrostatic devices in the microscopic scale; their fabrication has been possible thanks to the technology for Si‐integrated‐circuits. In particular, electrostatic micromotors have an increasing role as position actuators when submillimetric movements are required. Methodologies of numerical simulation applied to microdevices are a helpful tool for the designer, who should fulfil criteria often in mutual clash like electromechanical response and fabrication cost. More generally, procedures of automated optimal design are now available, tackling the design problem as the constrained minimization of an objective function suitably set up.

Fire Propagation in Vertical Stick Arrays - the Effects of Wind

A simple geometrical model of fire spread through arrays of vertically mounted fuel elements performs well in the absence of wind. The theory assumes that an adjacent fuel element ignites when the flame from the previous fuel element moves downward sufficiently that its temperature isotherm corresponding to the temperature of ignition intersects the top of the adjacent fuel element. This simple geometrical model is extended to incorporate the effects of wind, and its predictions are compared to wind tunnel observations of burning arrays. The model performs well at low wind speeds, but underestimates the wind speed at which the flame makes contact with adjacent fuel elements. The reason for this underestimate is likely to arise because of a weakness in one or more of the assumptions concerning, (1) the laminar nature of the flame, (2) the constancy of the flame height as the wind increases, or (3) the existence of a constant ignition temperature. The most significant finding is that this simple conceptual theory indicates that the rate of spread of a fire front as a result of wind is unlikely to be a simple function such as a power-law or an exponential, but is likely to be the solution to a set of differential equations that can be approximated by such simple functions over a portion of their range.