Articles de revues : « Dissipatio H.G »

1

Valandro, Leticia. « Clarice Lispector e a crítica Italiana ». Gláuks - Revista de Letras e Artes 20, n^o 2 (30 décembre 2020) : 78–98. http://dx.doi.org/10.47677/gluks.v20i2.193.

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O presente trabalho intenta apresentar um panorama da recepção crítica da obra de Clarice Lispector na Itália. Parte-se da primeira monografia publicada no país, na qual A Paixão segundo G. H. é comparada a Dissipatio H.G., de Guido Morselli. Além desta, analisam-se alguns artigos publicados em revistas especializadas, assim como o espaço dedicado por Luciana Stegagno Picchio a Clarice Lispector na sua Storia della letteratura brasiliana. Nessa, A hora da estrela é indicada como uma nova e incompleta fase literária aberta por Lispector e é sobre o romance que conta a tragédia de Macabéa que a crítica italiana, sobretudo, deteve-se. O que se pode observar é que, em oposição à grande e flórea quantidade de estudos que se realizam sobre a obra de Clarice Lispector, não somente no Brasil, mas também no exterior, a crítica italiana apresenta-se, ainda, bastante reduzida.

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Veignie, Etienne, et Catherine Rafin. « Efficiency of Penicillium canescens in Dissipating PAH in Industrial Aged Contaminated Soil Microcosms and Its Impact on Soil Organic Matter and Ecotoxicity ». Processes 10, n^o 3 (7 mars 2022) : 532. http://dx.doi.org/10.3390/pr10030532.

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The filamentous fungus Penicillium canescens, isolated from oil-polluted soil, was evaluated for its ability to dissipate high-molecular-weight polycyclic aromatic hydrocarbons (PAH). The study was conducted in a microcosm containing 180 g of historical PAH-contaminated soil under non-sterile conditions with two incubation temperatures (14 °C and 18 °C) on a 12-h cycle. The experiment was conducted over 8 months, with four experimental conditions created by varying the volumes of the bulking agent and vegetable oil (olive oil) and the time of addition of these compounds. The PAH dissipation performance of the fungal augmentation treatment was compared with that achieved with a biostimulated soil (bulking agent and vegetable oil) and with the untreated soil as control. The greatest PAH dissipation was obtained with P. canescens bioaugmentation (35.71% ± 1.73), with 13 of the 16 US EPA PAH significantly dissipated, at rates above 18%, and particularly high-molecular-weight PAH, composed of more than three fused aromatic rings. Nematode toxicity tests indicated a significant decrease in the toxicity of soil bioaugmented by this fungus. Fulvic and humic contents were significantly increased by this treatment. All these results suggest that bioaugmentation with P. canescens can be used to restore soils with long-term PAH contamination.

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Ungarish, Marius. « Benjamin’s gravity current into an ambient fluid with an open surface in a channel of general cross-section ». Journal of Fluid Mechanics 859 (27 novembre 2018) : 972–91. http://dx.doi.org/10.1017/jfm.2018.820.

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We present the solution of the idealized steady-state gravity current of height $h$ and density $\unicode[STIX]{x1D70C}_{1}$ that propagates into an ambient motionless fluid of height $H$ and density $\unicode[STIX]{x1D70C}_{2}$ in a channel of general non-rectangular cross-section, with an upper surface open to the atmosphere, at high Reynolds number. The current propagates with speed $U$ and causes a depth decrease $\unicode[STIX]{x1D712}$ of the top surface. This is a significant extension of Benjamin’s (J. Fluid Mech., vol. 31, 1968, pp. 209–248) seminal solution for the gravity current in a rectangular (or laterally unbounded) channel with a fixed top ($\unicode[STIX]{x1D712}=0$). The determination of $\unicode[STIX]{x1D712}$ is a part of the problem. Supposing that the direction of propagation is $x$ and gravity acceleration $g$ acts in the $-z$ direction, the sidewalls are specified by $y=-f_{I}(z)$ and $y=f_{II}(z),~z\in [0.H]$, and the width is $f(z)=f_{I}(z)+\,f_{II}(z)$. The dimensionless parameters of the problem are $a=h/H\in (0,1)$ and $r=\unicode[STIX]{x1D70C}_{2}/\unicode[STIX]{x1D70C}_{1}\in (0,1)$. We show that a control-volume analysis of the type used by Benjamin produces a system of algebraic equations for $\tilde{\unicode[STIX]{x1D712}}=\unicode[STIX]{x1D712}/H$ and $Fr=U/(g^{\prime }h)^{1/2}$ as functions of $a$ and $r$, where $g^{\prime }=(r^{-1}-1)g$ is the reduced gravity. The geometry enters the equation via the width function $f(z)$. We present solutions for typical $f(z)$: rectangle, semi-circle, $\vee$ triangle and trapezoid $\text{}\underline{/~\backslash }$ . The results are physically acceptable and insightful. The non-negative dissipation condition defines the domain of validity $a\leqslant a_{max}(r)$ (also depending on $f(z)$); the equality sign corresponds to energy-conserving cases. The critical speed limitation (with respect to the characteristics) is also considered briefly and suggests a slightly smaller $a\leqslant a_{crit}(r)$. The open-top results in the Boussinesq limit $r\rightarrow 1$ coincide with the fixed-top solution. Upon the reduction of $r$, for a fixed thickness $a$, the value of $Fr$ decreases and $\unicode[STIX]{x1D712}$ increases, until the point of energy-conserving (non-dissipative) flow; for smaller $r$, a negative non-physical dissipation appears. The trends are more pronounced for a converging cross-section geometry (like $\text{}\underline{/~\backslash }$ ) than for the opposite shape (like $\vee$ triangle). The previously investigated Benjamin-type steady-state $Fr$ and dissipation results are particular cases of the new formulation: $f(z)=$ const. reproduces the two-dimensional results, and $\unicode[STIX]{x1D712}=0$ recovers the fixed-top solution.

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PARACCHINI, C., et L. ROMANO'. « THE SCALING OF THE R(T) RESPONSE IN BSCCO (2212) FILMS AT LOW MAGNETIC FIELDS ». International Journal of Modern Physics B 14, n^o 25n27 (30 octobre 2000) : 2878–83. http://dx.doi.org/10.1142/s0217979200003034.

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The ratio V/I in three BSCCO (2212) films is studied at low magnetic fields (0.5-300 G). In the field-dependent region the data of R vs. Θ=[T-To(H))]/[Tm-To(H))] overlap on one line, where To(H) and Tm(H) are the limits of the process. The result is similar to the R(T,I) dependence in several planar superconductors and this coincidence indicates that low current and field play the same role in the dissipation of these materials. The R(T,I,H) dependence is approximated by R=Ro exp (- b /Θ0.5), suggesting that in these conditions the dissipation may be attributed to a single process due to the de-pairing of thermally excited vortex-antivortex pairs.

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Cao, Qi, Guoqing Ning, Fan Yang, Ye Wang, Bofeng Li et Xinlong Ma. « Hierarchically porous activated carbons prepared via a dissipative process : a high-capacity cathode for Li-ion capacitors ». Nanoscale 14, n^o 3 (2022) : 691–99. http://dx.doi.org/10.1039/d1nr05506b.

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Hierarchically porous activated carbons (PACs) are synthesized by a tableting-activation method. As a cathode for LICs, the optimal PACs exhibit an ultrahigh specific capacity of 251 mA h g−1 at 0.5 A g−1 and still retain 158 mA h g−1 at 15 A g−1.

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6

Guozhu, Song. « Asymptotic behaviour of non-autonomous dissipative systems in Hilbert space ». Journal of the Australian Mathematical Society. Series A. Pure Mathematics and Statistics 62, n^o 1 (février 1997) : 93–103. http://dx.doi.org/10.1017/s1446788700000574.

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AbstractIn this paper we discuss the asymptotic behaviour, as t → ∞, of the integral solution u(t) of the non-linear evolution equation where {A(t)}t≥0 is a family of m-dissipative operators in a Hilbert space H, and g ∈ Lloc (0, ∞ H).We give some sufficient conditions and some sufficient and necessary conditions to ensure that are weakly convergent.

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Cavalcanti, Marcelo M., Valéria N. Domingos Cavalcanti, Irena Lasiecka et Claudete M. Webler. « Intrinsic decay rates for the energy of a nonlinear viscoelastic equation modeling the vibrations of thin rods with variable density ». Advances in Nonlinear Analysis 6, n^o 2 (1 mai 2017) : 121–45. http://dx.doi.org/10.1515/anona-2016-0027.

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AbstractWe consider the long-time behavior of a nonlinear PDE with a memory term which can be recast in the abstract form$\frac{d}{dt}\rho(u_{t})+Au_{tt}+\gamma A^{\theta}u_{t}+Au-\int_{0}^{t}g(s)Au(t% -s)=0,$where A is a self-adjoint, positive definite operator acting on a Hilbert space H, ${\rho(s)}$ is a continuous, monotone increasing function, and the relaxation kernel ${g(s)}$ is a continuous, decreasing function in ${L_{1}(\mathbb{R}_{+})}$ with ${g(0)>0}$. Of particular interest is the case when ${A=-\Delta}$ with appropriate boundary conditions and ${\rho(s)=|s|^{\rho}s}$. This model arises in the context of solid mechanics accounting for variable density of the material. While finite energy solutions of the underlying PDE solutions exhibit exponential decay rates when strong damping is active (${\gamma>0,\theta=1}$), this uniform decay is no longer valid (by spectral analysis arguments) for dynamics subjected to frictional damping only, say, ${\theta=0}$ and ${g=0}$. In the absence of mechanical damping (${\gamma=0}$), the linearized version of the model reduces to a Volterra equation generated by bounded generators and, hence, it is exponentially stable for exponentially decaying kernels. The aim of the paper is to study intrinsic decays for the energy of the nonlinear model accounting for large classes of relaxation kernels described by the inequality ${g^{\prime}+H(g)\leq 0}$ with H convex and subject to the assumptions specified in (1.13) (a general framework introduced first in [1] in the context of linear second-order evolution equations with memory). In the context of frictional damping, such a framework was introduced earlier in [15], where it was shown that the decay rates of second-order evolution equations with frictional damping can be described by solutions of an ODE driven by a suitable convex function H which captures the behavior at the origin of the dissipation. The present paper extends this analysis to nonlinear equations with viscoelasticity. It is shown that the decay rates of the energy are intrinsically described by the solution of the dissipative ODE${S_{t}+c_{1}H(c_{2}S)=0}$with given intrinsic constants ${c_{1},c_{2}>0}$. The results obtained are sharp and they improve (by introducing a novel methodology) previous results in the literature (see [20, 19, 21, 6]) with respect to (i) the criticality of the nonlinear exponent ρ and (ii) the generality of the relaxation kernel.

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Kaminski, A. K., C. P. Caulfield et J. R. Taylor. « Nonlinear evolution of linear optimal perturbations of strongly stratified shear layers ». Journal of Fluid Mechanics 825 (20 juillet 2017) : 213–44. http://dx.doi.org/10.1017/jfm.2017.396.

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The Miles–Howard theorem states that a necessary condition for normal-mode instability in parallel, inviscid, steady stratified shear flows is that the minimum gradient Richardson number, $Ri_{g,min}$, is less than $1/4$ somewhere in the flow. However, the non-normality of the Navier–Stokes and buoyancy equations may allow for substantial perturbation energy growth at finite times. We calculate numerically the linear optimal perturbations which maximize the perturbation energy gain for a stably stratified shear layer consisting of a hyperbolic tangent velocity distribution with characteristic velocity $U_{0}^{\ast }$ and a uniform stratification with constant buoyancy frequency $N_{0}^{\ast }$. We vary the bulk Richardson number $Ri_{b}=N_{0}^{\ast 2}h^{\ast 2}/U_{0}^{\ast 2}$ (corresponding to $Ri_{g,min}$) between 0.20 and 0.50 and the Reynolds numbers $\mathit{Re}=U_{0}^{\ast }h^{\ast }/\unicode[STIX]{x1D708}^{\ast }$ between 1000 and 8000, with the Prandtl number held fixed at $\mathit{Pr}=1$. We find the transient growth of non-normal perturbations may be sufficient to trigger strongly nonlinear effects and breakdown into small-scale structures, thereby leading to enhanced dissipation and non-trivial modification of the background flow even in flows where $Ri_{g,min}>1/4$. We show that the effects of nonlinearity are more significant for flows with higher $\mathit{Re}$, lower $Ri_{b}$ and higher initial perturbation amplitude $E_{0}$. Enhanced kinetic energy dissipation is observed for higher-$Re$ and lower-$Ri_{b}$ flows, and the mixing efficiency, quantified here by $\unicode[STIX]{x1D700}_{p}/(\unicode[STIX]{x1D700}_{p}+\unicode[STIX]{x1D700}_{k})$ where $\unicode[STIX]{x1D700}_{p}$ is the dissipation rate of density variance and $\unicode[STIX]{x1D700}_{k}$ is the dissipation rate of kinetic energy, is found to be approximately 0.35 for the most strongly nonlinear cases.

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Alcantara-Licudine, Jocelyn P., Ngoc Lan Bui, Qing X. Li, Grant T. McQuate et Steven L. Peck. « Method for Determination of Xanthene Dyes in Guava Fruits and Its Application in a Field Dissipation Study ». Journal of AOAC INTERNATIONAL 83, n^o 3 (1 mai 2000) : 563–68. http://dx.doi.org/10.1093/jaoac/83.3.563.

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Abstract Xanthene dyes, i.e., phloxine B and uranine or phloxine B alone, are phototoxic to tephritid fruit flies infesting guava fruits. An analytical method was developed for determination of residues of these dyes used in bait solutions for suppression of the tephritid fruit fly population in guava fruits. The procedure involved solvent extraction, anionexchange cleanup, and determination by liquid chromatography or capillary zone electrophoresis. The dyes were extracted from 50 g guava fruit at 45°C with 400 mL methanol–acetonitrile (1 + 1) and 5 g magnesium oxide added as an alkaline and clarifying agent. The guava extract was adjusted to pH 8.5 and subjected to an amino column cleanup. Average recoveries of xanthene dyes added to guava purees ranged from 77 to 99% for phloxine B and from 79 to 102% for uranine at spiking levels of 0.05–1.00 μg/g. The method was applied to the determination of phloxine B residues in guava fruits collected from a dye-sprayed orchard. After phloxine B was applied at a rate of 62.5 g/ha for 14 weekly sprayings, it was found on guava fruits at an average concentration of 111 ± 18 ng/g 4 h after the 11th spraying. The concentration of phloxine B was 426 ± 94 ng/g in selected fruits with high deposits of the dye 4 h after spraying. Average concentrations of phloxine B 5 days after the 7th and 14th sprayings were 29 ± 7 and 19 ± 8 ng/g, respectively.

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Wolf, B., et G. Walsberg. « Respiratory and cutaneous evaporative water loss at high environmental temperatures in a small bird ». Journal of Experimental Biology 199, n^o 2 (1 février 1996) : 451–57. http://dx.doi.org/10.1242/jeb.199.2.451.

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We measured rates of respiratory and cutaneous evaporative water loss as a function of air temperature in a small desert bird, the verdin Auriparus flaviceps. Birds were placed in a two-compartment metabolic chamber that separately collected water evaporated from the bird's head and body. Cutaneous and respiratory evaporative water loss, as well as CO2 production, were measured in resting birds at 2 °C intervals between 30 and 50 °C. Metabolic rate was lowest at 38 °C (19 mW g-1) and increased to 28 mW g-1 at 50 °C. At the lowest air temperature, 30 °C, resting metabolic rate was 34 mW g-1. As air temperature increased from 30 to 50 °C, cutaneous water loss increased from 3.3 to 10.3 mg g-1 h-1 and respiratory water loss increased from 2.1-64.1 mg g-1 h-1. At moderate air temperatures (30-36 °C), water loss was divided almost evenly between respiratory and cutaneous components. As air temperature increased, however, verdins became heavily dependent on respiratory evaporation for heat dissipation. Evaporative water loss data for other species at high air temperatures suggest that partitioning of water loss may follow two different patterns. Evaporative heat dissipation may depend primarily on either cutaneous or respiratory modes of evaporative heat transfer. The physiological mechanisms and functional significance of these contrasting patterns of evaporative heat loss remain unknown.

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Mohan, T. S., Marouane Temimi, R. S. Ajayamohan, Narendra Reddy Nelli, Ricardo Fonseca, Michael Weston et Vineeth Valappil. « On the Investigation of the Typology of Fog Events in an Arid Environment and the Link with Climate Patterns ». Monthly Weather Review 148, n^o 8 (10 juillet 2020) : 3181–202. http://dx.doi.org/10.1175/mwr-d-20-0073.1.

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Abstract The central aim of this work is to investigate the characteristics of fog events over the United Arab Emirates (UAE) and identify the underlying physical processes responsible for fog initiation and dissipation. To achieve this, hourly meteorological measurements at eight airport stations, along with ERA5 reanalysis data (1995–2018), are utilized. The analysis indicates the dominance of radiation fog (RAD) as, on average, 70% of the observed events fall under this category. Fog in the UAE typically forms between 2000 and 0200 local time (LT) and dissipates between 0600 and 0900 LT. During a typical dense fog event recorded during 22–23 December 2017, cooling and moistening tendencies of up to 1.2 K h−1 and 0.7 g kg−1 h−1 are observed ~5–6 h before fog onset. In the vertical, a dry and warm layer above 750 hPa gradually descends from above 500 hPa to promote the development of fog. Similar conclusions are reached when analyzing composites of fog events. Further, the variability of fog occurrence associated with El Niño–Southern Oscillation (ENSO) patterns is explored. It is concluded that the El Niño (warm) and La Niña (cold) phases exhibit very different spatial characteristics with respect to surface meteorological variables. In particular, during El Niño events, the near-surface atmosphere is cooler and moister compared to La Niña events, favoring RAD fog formation over the UAE. Besides, fog events during El Niño years tend to last longer compared to La Niña years due to an earlier onset.

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UNGARISH, MARIUS. « A non-dissipative solution of Benjamin-type gravity current for a wide range of depth ratios ». Journal of Fluid Mechanics 682 (30 juin 2011) : 54–65. http://dx.doi.org/10.1017/jfm.2011.234.

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We consider the steady-state propagation of a high-Reynolds-number gravity current of height h and density ρc on the bottom of a horizontal channel of height H filled with ambient fluid of density ρa(<ρc), usually known as Benjamin's current problem. The objective is to derive an analytical result for the speed of propagation, U, in the form of the dimensionless Froude number, Fr(a) = U/(g′h)1/2). Here g′ = (ρc/ρa − 1)g is the reduced gravity-driving effect (g being the gravity acceleration) and a = h/H is the depth (thickness) ratio of the layer of the current to that of the ambient fluid into which the current propagates. The analysis is performed in a frame of reference attached to the current; in this frame the current is a motionless slug. The original analysis of Benjamin assumes that the speed of the ambient in the domain above the parallel-horizontal main part of the current (behind the head) is independent of the vertical coordinate z, but here we assume that a small u′(z) fluctuation about the depth-averaged speed u exists. Then, we impose the balances of volume flux, flow-force (momentum flux) and global energy conservation, for a control volume attached to the current. We show that this gives a unique analytical result for Fr as a function of a = h/H. We recall that the original counterpart solution FrB(a) of Benjamin does not satisfy the above-mentioned energy conservation condition, i.e. the system displays energy dissipation (except for the half-depth current case a = 1/2). The present dissipationless-flow Fr(a) result is valid for any a ≤ 1/2, i.e. currents of at most half-depth of the channel height. On the other hand, in agreement with Benjamin's solution, gravity currents of more than half-depth of the channel height require an energy source and are impossible in normal conditions. The new Fr(a) is slightly smaller than Benjamin's FrB(a) result for 0 < a < 1/2, and the difference vanishes at a = 1/2 and a → 0 (a current of finite height in a very deep ambient).

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Yuan, Huichin, Edward P. Ingenito et Béla Suki. « Dynamic properties of lung parenchyma : mechanical contributions of fiber network and interstitial cells ». Journal of Applied Physiology 83, n^o 5 (1 novembre 1997) : 1420–31. http://dx.doi.org/10.1152/jappl.1997.83.5.1420.

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Yuan, Huichin, Edward P. Ingenito, and Béla Suki.Dynamic properties of lung parenchyma: mechanical contributions of fiber network and interstitial cells. J. Appl. Physiol. 83(5): 1420–1431, 1997.—We investigated the contributions of the connective tissue fiber network and interstitial cells to parenchymal mechanics in a surfactant-free system. In eight strips of uniform dimension from guinea pig lung, we assessed the storage (G′) and loss (G”) moduli by using pseudorandom length oscillations containing a specially designed set of seven frequencies from 0.07 to 2.4 Hz at baseline, during methacholine (MCh) challenge, and after death of the interstitial cells. Measurements were made at mean forces of 0.5 and 1 g and strain amplitudes of 5, 10, and 15% and were repeated 12 h later in the same, but nonviable samples. The results were interpreted using a linear viscoelastic model incorporating both tissue damping (G) and stiffness (H). The G′ and G” increased linearly with the logarithm of frequency, and both G and H showed negative strain amplitude and positive mean force dependence. After MCh challenge, the G′ and G” spectra were elevated uniformly, and G and H increased by <15%. Tissue stiffness, strain amplitude, and mean force dependence were virtually identical in the viable and nonviable samples. The G and hence energy dissipation were ∼10% smaller in the nonviable samples due to absence of actin-myosin cross-bridge cycling. We conclude that the connective tissue network may also dominate parenchymal mechanics in the intact lung, which can be influenced by the tone or contraction of interstitial cells.

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Wright, Terry R., Alex G. Ogg et E. Patrick Fuerst. « Dissipation and Water Activation of UCC-C4243 ». Weed Science 43, n^o 1 (mars 1995) : 149–55. http://dx.doi.org/10.1017/s0043174500080966.

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Field experiments were conducted in 1992 and 1993 to determine the timing and amount of rainfall required to activate UCC-C4243 applied preemergence. UCC-C4243 at 0, 70, and 140 g ai ha−1was applied 1, 7, 14, and 21 d before 0.5 or 2 cm of simulated rainfall. Temporary rainshelters protected field plots from natural rainfall during the 21 d dry period. Herbicide activity was determined in the field by seeding lentil, wheat, common lambsquarters, and field pennycress and in the greenhouse by a sugarbeet bioassay of soil samples (0 to 3 cm depth) taken from all plots immediately before irrigation. UCC-C4243 did not injure wheat; however, lentil population was reduced when simulated rainfall occurred within 7 d after application. Lentil injury was greater with higher herbicide rate and higher water level. UCC-C4243 at 70 and 140 g ha−1reduced populations of both weed species by 75 and 90%, respectively, when either 0.5 or 2 cm simulated rainfall was received within 1 d after herbicide application. Weed control was reduced with a 21 d delay between herbicide application and water activation. The sugarbeet bioassay showed a linear decrease of herbicide activity over time and also with accumulated photosynthetically active radiation. After 17.9 d, herbicide activity on a dry soil surface decreased 50%. Laboratory investigations show that [14C]-UCC-C4243 on glass slides was photodegraded by near ultraviolet light (290 to 400 nm). Volatilization of14C-labeled herbicide from glass slides was less than 5% after exposure to turbulent air for 48 h.

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Trejo, Adriana Morales, Fernanda González, Hugo Bernal, Miguel Cervantes, Caroline Gonzalez-Vega et John K. Htoo. « PSIX-26 Effect of supplemental Arg on respiration rate and body temperature of pigs exposed to heat stress ». Journal of Animal Science 97, Supplement_3 (décembre 2019) : 351. http://dx.doi.org/10.1093/jas/skz258.699.

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Abstract Heat stress (HS) reduces feed intake and affects the well-being of pigs by increasing their body temperature (BT) and respiration rate (RR). Nitric oxide, an Arg metabolite, helps to dissipate body heat by stimulating blood vasodilation. Because reduced feed intake translates into decreased Arg consumption, the effect of supplementing Arg in the diet on BT and RR was analyzed using 8-ileal cannulated pigs (61.7±2.7 kg BW) exposed to HS. A thermometer set to register BT at 5-min intervals was implanted into the ileum. There were two treatments: control wheat-soybean meal plus free Lys-Thr diet (CON), and the CON diet added with 0.20% free Arg (ARG). The study was conducted in two-6 d periods; d1-d3 for diet adaptation and d4-d6 for BT data analysis. The RR (respirations per min - rpm) was measured in all pigs at 0600-h and 1600-h. Pigs were fed at 0700-h and 1900-h, 900 g/meal. Ambient temperature and relative humidity were: 28.2-to-34.6 °C, 53-to-82%, respectively. Ambient temperature and BT followed a similar pattern every day. There was no interaction in BT and RR between periods. Overall, BT of ARG pigs (40.75°C) was slightly lower (P < 0.05) than in CON pigs (40.71°C). Arg supplementation greatly reduced RR (rpm) regardless of period and day time (P < 0.05): overall (91, 73), period-1 (98, 78), period-2 (85, 68), 0600-h, (68, 52), 1600-h (115, 94), respectively. The RR at 0600-h (60) was lower than at 1400-h (109; P < 0.05) regardless of diet. The reduced RR because of Arg supplementation may be explained as an increased synthesis of nitric oxide probably resulting in both increased vasodilation and dissipation of body heat. In conclusion, although supplemental Arg caused a modest decrease in BT, the large RR reduction may indicate that Arg might help to improve the welfare of HS pigs.

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HARDEWIG, I., A. D. F. ADDINK, M. K. GRIESHABER, H. O. PÖRTNER et G. VAN DEN THILLART. « Metabolic Rates at Different Oxygen Levels Determined by Direct and Indirect Calorimetry in the Oxyconformer Sipunculus Nudus ». Journal of Experimental Biology 157, n^o 1 (1 mai 1991) : 143–60. http://dx.doi.org/10.1242/jeb.157.1.143.

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Oxygen uptake and the mode of energy production in Sipunculus nudus L. were determined at different oxygen levels by means of direct and indirect calorimetry. Oxygen consumption declined linearly with decreasing ambient POO2 A similar decrease in heat production was observed down to a POO2 of 8.66 kPa. At lower oxygen tensions, a discrepancy between aerobic and total heat production indicated the onset of anaerobic metabolism. The occurrence of the critical POO2 between 8.66 and 2.66 kPa was confirmed by estimation of anaerobic end products in the body wall musculature. The contributions of aerobic and anaerobic metabolism to total ATP production were determined at a POO2 of 2.66 kPa and were found to be 48 and 52%, respectively. Measured heat dissipation under extreme hypoxia (POO2 nominally zero) (21.5±3.5 mJ h−1 g−1) agreed with the enthalpy changes calculated from the rates of formation of anaerobic end products (17.9±4.7 mJ h−1 g−1). For the sake of redox balance maintenance, saturation of fatty acids was assumed; this would be accompanied by an additional heat production of 3.3 mJ h−1 g−1, so that the total calculated enthalpy change amounted to 21.2 mJ h−1 g−1

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Mitzner, Wayne, et Elizabeth Wagner. « Letters to the Editor ». Journal of Applied Physiology 84, n^o 6 (1 juin 1998) : 2198–99. http://dx.doi.org/10.1152/jappl.1998.84.6.2198.

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The following is the abstract of the article discussed in the subsequent letter: Yuan, Huichin, Edward P. Ingenito, and Béla Suki. Dynamic properties of lung parenchyma: mechanical contributions of fiber network and interstitial cells. J. Appl. Physiol. 83(5): 1420–1431, 1997.—We investigated the contributions of the connective tissue fiber network and interstitial cells to parenchymal mechanics in a surfactant-free system. In eight strips of uniform dimension from guinea pig lung, we assessed the storage (G′) and loss (G") moduli by using pseudo-random length oscillations containing a specially designed set of seven frequencies from 0.07 to 2.4 Hz at baseline, during methacholine (MCh) challenge, and after death of the interstitial cells. Measurements were made at mean forces of 0.5 and 1 g and strain amplitudes of 5, 10, and 15% and were repeated 12 h later in the same, but nonviable samples. The results were interpreted using a linear viscoelastic model incorporating both tissue damping (G) and stiffness (H). The G′ and G" increased linearly with the logarithm of frequency, and both G and H showed negative strain amplitude and positive mean force dependence. After MCh challenge, the G′ and G" spectra were elevated uniformly, and G and H increased by <15%. Tissue stiffness, strain amplitude, and mean force dependence were virtually identical in the viable and nonviable samples. The G and hence energy dissipation were ∼10% smaller in the nonviable samples due to absence of actin-myosin cross-bridge cycling. We conclude that the connective tissue network may also dominate parenchymal mechanics in the intact lung, which can be influenced by the tone or contraction of interstitial cells.

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BHALLA, G. L., PRATIMA et AMITA MALIK. « MODIFIED AMBEGAOKAR–HALPERIN MODEL AND DISSIPATION IN THE POLYCRYSTALLINE Ba2YCu3O7-δ SUPERCONDUCTOR ». Modern Physics Letters B 18, n^o 02n03 (10 février 2004) : 99–103. http://dx.doi.org/10.1142/s0217984904006718.

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The magnetoresistance curves of polycrystalline Ba 2 YCu 3 O 7-δ samples for H=0, 1050 and 4880 G are analyzed using the modified Ambegaokar–Halperin model. The analysis shows the occurrence of a crossover in the R–T curves at a field dependent temperature T BP , revealing that the dissipation in Ba 2 YCu 3 O 7-δ samples is possibly caused by two different mechanisms: vortex-dynamics in the low temperature region (below T BP ) and the order parameter fluctuations in the high temperature region (above T BP ).

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Wang, Hui, Zhi-Fu Gao, Huan-Yu Jia, Na Wang et Xiang-Dong Li. « Estimation of Electrical Conductivity and Magnetization Parameter of Neutron Star Crusts and Applied to the High-Braking-Index Pulsar PSR J1640-4631 ». Universe 6, n^o 5 (1 mai 2020) : 63. http://dx.doi.org/10.3390/universe6050063.

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Young pulsars are thought to be highly magnetized neutron stars (NSs). The crustal magnetic field of a NS usually decays at different timescales in the forms of Hall drift and Ohmic dissipation. The magnetization parameter ω B τ is defined as the ratio of the Ohmic timescale τ O h m to the Hall drift timescale τ H a l l . During the first several million years, the inner temperature of the newly born neutron star cools from T = 10 9 K to T = 1.0 × 10 8 K, and the crustal conductivity increases by three orders of magnitude. In this work, we adopt a unified equations of state for cold non-accreting neutron stars with the Hartree–Fock–Bogoliubov method, developed by Pearson et al. (2018), and choose two fiducial dipole magnetic fields of B = 1.0 × 10 13 G and B = 1.0 × 10 14 G, four different temperatures, T, and two different impurity concentration parameters, Q, and then calculate the conductivity of the inner crust of NSs and give a general expression of magnetization parameter for young pulsars: ω B τ ≃ ( 1 − 50 ) B 0 / ( 10 13 G) by using numerical simulations. It was found when B ≤ 10 15 G, due to the quantum effects, the conductivity increases slightly with the increase in the magnetic field, the enhanced magnetic field has a small effect on the matter in the low-density regions of the crust, and almost has no influence the matter in the high-density regions. Then, we apply the general expression of the magnetization parameter to the high braking-index pulsar PSR J1640-4631. By combining the observed arrival time parameters of PSR J1640-4631 with the magnetic induction equation, we estimated the initial rotation period P 0 , the initial dipole magnetic field B 0 , the Ohm dissipation timescale τ O h m and Hall drift timescale τ H a l l . We model the magnetic field evolution and the braking-index evolution of the pulsar and compare the results with its observations. It is expected that the results of this paper can be applied to more young pulsars.

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Carmagnola, Irene, Valeria Chiono, Gerardina Ruocco, Annachiara Scalzone, Piergiorgio Gentile, Paola Taddei et Gianluca Ciardelli. « PLGA Membranes Functionalized with Gelatin through Biomimetic Mussel-Inspired Strategy ». Nanomaterials 10, n^o 11 (2 novembre 2020) : 2184. http://dx.doi.org/10.3390/nano10112184.

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Electrospun membranes have been widely used as scaffolds for soft tissue engineering due to their extracellular matrix-like structure. A mussel-inspired coating approach based on 3,4-dihydroxy-DL-phenylalanine (DOPA) polymerization was proposed to graft gelatin (G) onto poly(lactic-co-glycolic) acid (PLGA) electrospun membranes. PolyDOPA coating allowed grafting of gelatin to PLGA fibers without affecting their bulk characteristics, such as molecular weight and thermal properties. PLGA electrospun membranes were dipped in a DOPA solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 7 h and then incubated in G solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 16 h. PLGA fibers had an average diameter of 1.37 ± 0.23 µm. Quartz crystal microbalance with dissipation technique (QCM-D) analysis was performed to monitor DOPA polymerization over time: after 7 h the amount of deposited polyDOPA was 71 ng/cm2. After polyDOPA surface functionalization, which was, also revealed by Raman spectroscopy, PLGA membranes maintained their fibrous morphology, however the fiber size and junction number increased. Successful functionalization with G was demonstrated by FTIR-ATR spectra, which showed the presence of G adsorption bands at 1653 cm−1 (Amide I) and 1544 cm−1 (Amide II) after G grafting, and by the Kaiser Test, which revealed a higher amount of amino groups for G functionalized membranes. Finally, the biocompatibility of the developed substrates and their ability to induce cell growth was assessed using Neonatal Normal Human Dermal Fibroblasts.

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HACKER, J. N., et P. F. LINDEN. « Gravity currents in rotating channels. Part 1. Steady-state theory ». Journal of Fluid Mechanics 457 (18 avril 2002) : 295–324. http://dx.doi.org/10.1017/s0022112001007662.

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A theory is developed for the speed and structure of steady-state non-dissipative gravity currents in rotating channels. The theory is an extension of that of Benjamin (1968) for non-rotating gravity currents, and in a similar way makes use of the steady-state and perfect-fluid (incompressible, inviscid and immiscible) approximations, and supposes the existence of a hydrostatic ‘control point’ in the current some distance away from the nose. The model allows for fully non-hydrostatic and ageostrophic motion in a control volume V ahead of the control point, with the solution being determined by the requirements, consistent with the perfect-fluid approximation, of energy and momentum conservation in V, as expressed by Bernoulli's theorem and a generalized flow-force balance. The governing parameter in the problem, which expresses the strength of the background rotation, is the ratio W = B/R, where B is the channel width and R = (g′H)1/2/f is the internal Rossby radius of deformation based on the total depth of the ambient fluid H. Analytic solutions are determined for the particular case of zero front-relative flow within the gravity current. For each value of W there is a unique non-dissipative two-layer solution, and a non-dissipative one-layer solution which is specified by the value of the wall-depth h0. In the two-layer case, the non-dimensional propagation speed c = cf(g′H)−1/2 increases smoothly from the non-rotating value of 0.5 as W increases, asymptoting to unity for W → ∞. The gravity current separates from the left-hand wall of the channel at W = 0.67 and thereafter has decreasing width. The depth of the current at the right-hand wall, h0, increases, reaching the full depth at W = 1.90, after which point the interface outcrops on both the upper and lower boundaries, with the distance over which the interface slopes being 0.881R. In the one-layer case, the wall-depth based propagation speed Froude number c0 = cf(g′h0)−1/2 = 21/2, as in the non-rotating one-layer case. The current separates from the left-hand wall of the channel at W0 ≡ B/R0 = 2−1/2, and thereafter has width 2−1/2R0, where R0 = (g′h0)1/2/f is the wall-depth based deformation radius.

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Bukunt, Brandon P., et Gary M. Barnes. « The Subtropical Jet Stream Delivers the Coup de Grâce to Hurricane Felicia (2009) ». Weather and Forecasting 30, n^o 4 (1 août 2015) : 1039–49. http://dx.doi.org/10.1175/waf-d-15-0004.1.

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Abstract The NOAA Gulfstream IV (G-IV) routinely deploys global positioning system dropwindsondes (GPS sondes) to sample the environment around hurricanes that threaten landfall in the United States and neighboring countries. Part of this G-IV synoptic surveillance flight pattern is a circumnavigation 300–350 km from the circulation center of the hurricane. Here, the GPS sondes deployed over two consecutive days around Hurricane Felicia (2009) as it approached Hawaii are examined. The circumnavigations captured only the final stages of decay of the once-category-4 hurricane. Satellite images revealed a rapid collapse of the deep convection in the eyewall region and the appearance of the low-level circulation center over ~8 h. Midlevel dry air associated with the Pacific high was present along portions of the circumnavigation but did not reach the eyewall region during the period of rapid dissipation of the deep clouds. In contrast, the subtropical jet stream (STJ) enhanced the deep-layer vertical shear of the horizontal wind (VWS; 850–200 hPa) to greater than 30 m s−1 first in the northwest quadrant; ~6 h later the STJ was estimated to reach the eyewall region of the hurricane and was nearly coincident with the dissipation of deep convection in the core of Felicia. Felicia’s demise is an example of the STJ enhancing the VWS and inhibiting intense hurricanes from making landfall in Hawaii. The authors speculate that VWS calculated over quadrants rather than entire annuli around a hurricane may be more appropriate for forecasting intensity change.

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Wærsted, Eivind G., Martial Haeffelin, Jean-Charles Dupont, Julien Delanoë et Philippe Dubuisson. « Radiation in fog : quantification of the impact on fog liquid water based on ground-based remote sensing ». Atmospheric Chemistry and Physics 17, n^o 17 (14 septembre 2017) : 10811–35. http://dx.doi.org/10.5194/acp-17-10811-2017.

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Abstract. Radiative cooling and heating impact the liquid water balance of fog and therefore play an important role in determining their persistence or dissipation. We demonstrate that a quantitative analysis of the radiation-driven condensation and evaporation is possible in real time using ground-based remote sensing observations (cloud radar, ceilometer, microwave radiometer). Seven continental fog events in midlatitude winter are studied, and the radiative processes are further explored through sensitivity studies. The longwave (LW) radiative cooling of the fog is able to produce 40–70 g m−2 h−1 of liquid water by condensation when the fog liquid water path exceeds 30 g m−2 and there are no clouds above the fog, which corresponds to renewing the fog water in 0.5–2 h. The variability is related to fog temperature and atmospheric humidity, with warmer fog below a drier atmosphere producing more liquid water. The appearance of a cloud layer above the fog strongly reduces the LW cooling relative to a situation with no cloud above; the effect is strongest for a low cloud, when the reduction can reach 100 %. Consequently, the appearance of clouds above will perturb the liquid water balance in the fog and may therefore induce fog dissipation. Shortwave (SW) radiative heating by absorption by fog droplets is smaller than the LW cooling, but it can contribute significantly, inducing 10–15 g m−2 h−1 of evaporation in thick fog at (winter) midday. The absorption of SW radiation by unactivated aerosols inside the fog is likely less than 30 % of the SW absorption by the water droplets, in most cases. However, the aerosols may contribute more significantly if the air mass contains a high concentration of absorbing aerosols. The absorbed radiation at the surface can reach 40–120 W m−2 during the daytime depending on the fog thickness. As in situ measurements indicate that 20–40 % of this energy is transferred to the fog as sensible heat, this surface absorption can contribute significantly to heating and evaporation of the fog, up to 30 g m−2 h−1 for thin fog, even without correcting for the typical underestimation of turbulent heat fluxes by the eddy covariance method. Since the radiative processes depend mainly on the profiles of temperature, humidity and clouds, the results of this paper are not site specific and can be generalised to fog under different dynamic conditions and formation mechanisms, and the methodology should be applicable to warmer and moister climates as well. The retrieval of approximate emissivity of clouds above fog from cloud radar should be further developed.

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Liu, Zhiyu, S. A. Thorpe et W. D. Smyth. « Instability and hydraulics of turbulent stratified shear flows ». Journal of Fluid Mechanics 695 (20 février 2012) : 235–56. http://dx.doi.org/10.1017/jfm.2012.13.

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AbstractThe Taylor–Goldstein (T–G) equation is extended to include the effects of small-scale turbulence represented by non-uniform vertical and horizontal eddy viscosity and diffusion coefficients. The vertical coefficients of viscosity and diffusion, ${A}_{V} $ and ${K}_{V} $, respectively, are assumed to be equal and are expressed in terms of the buoyancy frequency of the flow, $N$, and the dissipation rate of turbulent kinetic energy per unit mass, $\varepsilon $, quantities that can be measured in the sea. The horizontal eddy coefficients, ${A}_{H} $ and ${K}_{H} $, are taken to be proportional to the dimensionally correct form, ${\varepsilon }^{1/ 3} {l}^{4/ 3} $, found appropriate in the description of horizontal dispersion of a field of passive markers of scale $l$. The extended T–G equation is applied to examine the stability and greatest growth rates in a turbulent shear flow in stratified waters near a sill, that at the entrance to the Clyde Sea in the west of Scotland. Here the main effect of turbulence is a tendency towards stabilizing the flow; the greatest growth rates of small unstable disturbances decrease, and in some cases flows that are unstable in the absence of turbulence are stabilized when its effects are included. It is conjectured that stabilization of a flow by turbulence may lead to a repeating cycle in which a flow with low levels of turbulence becomes unstable, increasing the turbulent dissipation rate and so stabilizing the flow. The collapse of turbulence then leads to a condition in which the flow may again become unstable, the cycle repeating. Two parameters are used to describe the ‘marginality’ of the observed flows. One is based on the proximity of the minimum flow Richardson number to the critical Richardson number, the other on the change in dissipation rate required to stabilize or destabilize an observed flow. The latter is related to the change needed in the flow Reynolds number to achieve zero growth rate. The unstable flows, typical of the Clyde Sea site, are relatively further from neutral stability in Reynolds number than in Richardson number. The effects of turbulence on the hydraulic state of the flow are assessed by examining the speed and propagation direction of long waves in the Clyde Sea. Results are compared to those obtained using the T–G equation without turbulent viscosity or diffusivity. Turbulence may change the state of a flow from subcritical to supercritical.

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Thi Kim Yen, Nguyen, Nguyen Quy Tuan, Ngoc Dat Trinh, Vu Truong Son Le, Ngoc Toan Dang, Anh Thi Le, Nguyen Tien Tran et Ngo Tran. « Detailed microwave absorption performance of BaFe₁₂O₁₉ nano-hexaplates with a large variety of thicknesses ». Advances in Natural Sciences : Nanoscience and Nanotechnology 13, n^o 2 (1 juin 2022) : 025006. http://dx.doi.org/10.1088/2043-6262/ac6c1f.

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Abstract We successfully prepared BaFe12O19 (BaM) nano-hexaplates using the co-precipitation method followed by heat treatment. The hexaplate-like grain size varied in the range of 50–200 nm, while its crystalline size was ∼46 nm. Before investigating microwave absorption, structural and magnetic properties were studied by x-ray diffraction, Raman scattering, and a vibrating sample magnetometer. The structural studies showed a pure phase of BaM, while the magnetic studies revealed a ferro/ferrimagnetic behaviour with M s = 59.93 emu g−1, M r = 32.49 emu g−1, and H c = 5.16 kOe. Microwave dissipation features were systemically investigated for device thickness of 0.25–10 mm with a measured frequency range of 2–16 GHz. The study showed that the BaFe12O19 sample could absorb more than 99.9% of the incident microwave in the 12–14 GHz frequency range for 6.5 mm thickness. The effective absorption bandwidth was also fairly large, as ∼3 GHz in this frequency range. The microwave dissipation features of BaM in this work were better than pure BaM ones in other studies and relatively comparable with BaM-based microwave absorbers. The magnetic loss originated from natural resonance, while the dielectric loss resulted from multi-interface, interface, and dipolar polarization. Overall, the BaFe12O19 sample in this study could be used as a promising microwave absorber in the Ku waveband.

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Pizzo, N. E., et W. Kendall Melville. « Vortex generation by deep-water breaking waves ». Journal of Fluid Mechanics 734 (8 octobre 2013) : 198–218. http://dx.doi.org/10.1017/jfm.2013.453.

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AbstractThe connection between wave dissipation by breaking deep-water surface gravity waves and the resulting turbulence and mixing is crucial for an improved understanding of air–sea interaction processes. Starting with the ensemble-averaged Euler equations, governing the evolution of the mean flow, we model the forcing, associated with the breaking-induced Reynolds shear stresses, as a body force describing the bulk scale effects of a breaking deep-water surface gravity wave on the water column. From this, we derive an equation describing the generation of circulation, $\Gamma $, of the ensemble-average velocity field, due to the body force. By examining the relationship between a breaking wave and an impulsively forced fluid, we propose a functional form for the body force, allowing us to build upon the classical work on vortex ring phenomena to both quantify the circulation generated by a breaking wave and describe the vortex structure of the induced motion. Using scaling arguments, we show that $\Gamma = \alpha {(hk)}^{3/ 2} {c}^{3} / g$, where ($c, h, k$) represent a characteristic speed, height and wavenumber of the breaking wave, respectively, $g$ is the acceleration due to gravity and $\alpha $ is a constant. This then allows us to find a direct relationship between the circulation and the wave energy dissipation rate per unit crest length due to breaking, ${\epsilon }_{l} $. Finally, we compare our model and the available experimental data.

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Fu, Shizuo, et Huiwen Xue. « The Effect of Ice Nuclei Efficiency on Arctic Mixed-Phase Clouds from Large-Eddy Simulations ». Journal of the Atmospheric Sciences 74, n^o 12 (27 novembre 2017) : 3901–13. http://dx.doi.org/10.1175/jas-d-17-0112.1.

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Abstract The effects of ice nuclei (IN) efficiency on the persistent ice formation in Arctic mixed-phase clouds (AMCs) are investigated using a large-eddy simulation model, coupled to a bin microphysics scheme with a prognostic IN formulation. In the three cases where the IN efficiency is high, ice formation and IN depletion are fast. When the IN concentration is 1 and 10 g−1, IN are completely depleted and the cloud becomes purely liquid phase before the end of the 24-h simulation. When the IN concentration is 100 g−1, the IN supply is sufficient but the liquid water is completely consumed so that the cloud dissipates quickly. In the three cases when the IN efficiency is low, ice formation is negligible in the first several hours but becomes significant as the temperature is decreased through longwave cooling. Before the end of the simulation, the cloud is in mixed phase when the IN concentration is 1 and 10 g−1 but dissipates when the IN concentration is 100 g−1. In the case where two types of IN are considered, ice formation persists throughout the simulation. Analysis shows that as the more efficient IN are continuously removed through ice formation, the less efficient IN gradually nucleate more ice crystals because the longwave cooling decreases the cloud temperature. This mechanism is further illustrated with a simple model. These results indicate that a spectrum of IN efficiency is necessary to maintain the persistent ice formation in AMCs.

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Hirai, T., K. A. McKeown, R. F. M. Gomes et J. H. T. Bates. « Effects of lung volume on lung and chest wall mechanics in rats ». Journal of Applied Physiology 86, n^o 1 (1 janvier 1999) : 16–21. http://dx.doi.org/10.1152/jappl.1999.86.1.16.

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To investigate the effect of lung volume on chest wall and lung mechanics in the rats, we measured the impedance (Z) under closed- and open-chest conditions at various positive end-expiratory pressures (0–0.9 kPa) by using a computer-controlled small-animal ventilator (T. F. Schuessler and J. H. T. Bates. IEEE Trans. Biomed. Eng. 42: 860–866, 1995) that we have developed for determining accurately the respiratory Z in small animals. The Z of total respiratory system and lungs was measured with small-volume oscillations between 0.25 and 9.125 Hz. The measured Z was fitted to a model that featured a constant-phase tissue compartment (with dissipation and elastance characterized by constants G and H, respectively) and a constant airway resistance (Z. Hantos, B. Daroczy, B. Suki, S. Nagy, and J. J. Fredberg. J. Appl. Physiol. 72: 168–178, 1992). We matched the lung volume between the closed- and open-chest conditions by using the quasi-static pressure-volume relationship of the lungs to calculate Z as a function of lung volume. Resistance decreased with lung volume and was not significantly different between total respiratory system and lungs. However, G and H of the respiratory system were significantly higher than those of the lungs. We conclude that chest wall in rats has a significant influence on tissue mechanics of the total respiratory system.

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GLASHEEN, J. S., et STEVEN C. HAND. « Metabolic Heat Dissipation and Internal Solute Levels of Artemia Embryos During Changes in Cell-Associated Water ». Journal of Experimental Biology 145, n^o 1 (1 septembre 1989) : 263–82. http://dx.doi.org/10.1242/jeb.145.1.263.

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Embryos (cysts) of the brine shrimp Artemia enter a profound, yet reversible, state of metabolic arrest in response to cellular dehydration. We have monitored metabolic activity during this transition in embryos from the Great Salt Lake population by using microcalorimetric measurements of heat dissipation. Embryo hydration states can be precisely controlled by immersing cysts in solutions of varying ionic strength. When developing embryos were incubated in a 2.0moll−1NaCl solution, heat dissipation fell after 20 h to 1.13 mWg−1 dry mass, or 21 % of the value obtained when embryos were in control solutions of 0.25 moll−1. At higher ionic concentrations, heat dissipation declined to as low as 3% of control values. Recovery from dehydration was rapid. Energy flow increased to 135% of control values within 2h after returning cysts to the control medium. These metabolic transitions were correlated with embryo hydration levels measured across the same dehydration series. Total cyst water ranged from 112±2.6 gH2O 100 g−1 dry mass in 0.25 mol l−1 NaCl to 46±0.6 gH2O 100 g−1 dry mass in 5.0 mol l−1 NaCl. At the first point where heat dissipation was markedly suppressed (the 2.0 mol l−1 incubation), cyst water content was 72.8 ±0.9 gH2O 100 g−1 dry mass. This water content is similar to the ‘critical’ hydration level required to suppress carbohydrate catabolism and respiration in San Francisco Bay Artemia embryos (Clegg, 1976a,b). However, hydration characteristics of the two populations differed in solutions of lower ionic concentration. Total osmotic pressure in fully hydrated cysts was 1300 mosmol kg−1 H2O. A comprehensive inventory of the internal osmolytes indicated that inorganic ions (Na+, K+, Cl−, Mg2+, Ca2+, Pi) accounted for 21% of the osmotic activity and 1.48% of embryo dry mass. Organic solutes (trehalose, glycerol, ninhydrinpositive substances, and trimethylamine-N-oxide+betaine) contributed 60% of the osmotic pressure and 22% of the dry mass. Macromolecular components (protein, lipids, glycogen and DNA) were also quantified and formed the bulk of embryo mass. Taken together, 97.4% of the cyst dry mass was identified. At the cellular dehydration state promoting metabolic arrest, the concentrations of inorganic and organic osmolytes were 480–590 mmol kg−1 H2O and 1200–1480 mmol kg−1 H2O, respectively. The influence of these osmolyte concentrations is considered in the context of macromolecular assembly and metabolic control.

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Kumaran, V. « Stability of the flow of a fluid through a flexible tube at high Reynolds number ». Journal of Fluid Mechanics 302 (10 novembre 1995) : 117–39. http://dx.doi.org/10.1017/s0022112095004034.

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The stability of the Hagen-Poiseuille flow of a Newtonian fluid in a tube of radius R surrounded by an incompressible viscoelastic medium of radius R < r < HR is analysed in the high Reynolds number regime. The dimensionless numbers that affect the fluid flow are the Reynolds number Re = (ρVR / η), the ratio of the viscosities of the wall and fluid ηr = (ηs/η), the ratio of radii H and the dimensionless velocity Γ = (ρV2/G)1/2. Here ρ is the density of the fluid, G is the coefficient of elasticity of the wall and Vis the maximum fluid velocity at the centre of the tube. In the high Reynolds number regime, an asymptotic expansion in the small parameter ε = (1/Re) is employed. In the leading approximation, the viscous effects are neglected and there is a balance between the inertial stresses in the fluid and the elastic stresses in the medium. There are multiple solutions for the leading-order growth rate do), all of which are imaginary, indicating that the fluctuations are neutrally stable, since there is no viscous dissipation of energy or transfer of energy from the mean flow to the fluctruations due to the Reynolds strees.There is an O(ε1/2) correction to the growth rate, s(1), due to the presence of a wall layer of thickness ε1/2R where the viscous stresses are O(ε1/2) smaller than the inertial stresses. An energy balance analysis indicates that the transfer of energy from the mean flow to the fluctuations due to the Reynolds stress in the wall layer is exactly cancelled by an opposite transfer of equal magnitude due to the deformation work done at the interface, and there is no net transfer from the mean flow to the fluctuations. Consequently, the fluctuations are stabilized by the viscous dissipation in the wall layer, and the real part of s(1) is negative. However, there are certain values of Γ and wavenumber k where s(l) = 0. At these points, the wail layer amplitude becomes zero because the tangential velocity boundary condition is identically satisfied by the inviscid flow solution. The real part of the O(ε) correction to the growth rate s(2) turns out to be negative at these points, indicating a small stabilizing effect due to the dissipation in the bulk of the fluid and the wall material. It is found that the minimum value of s(2) increases ∝ (H − 1)−2 for (H − 1) [Lt ] 1 (thickness of wall much less than the tube radius), and decreases ∝ (H−4 for H [Gt ] 1. The damping rate for the inviscid modes is smaller than that for the viscous wall and centre modes in a rigid tube, which have been determined previously using a singular perturbation analysis. Therefore, these are the most unstable modes in the flow through a flexible tube.

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Rabello, Tania Nunes. « Decay of solutions of a nonlinear hyperbolic system in noncylindrical domain ». International Journal of Mathematics and Mathematical Sciences 17, n^o 3 (1994) : 561–70. http://dx.doi.org/10.1155/s0161171294000815.

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In this paper we study the existence of solutions of the following nonlinear hyperbolic svstem|u″+A(t)u+b(x)G(u)=f in Qu=0 on Σu(0)=uο u1(0)=u1whereQis a noncylindrical domain ofℝn+1with lateral boundaryΣ,u−(u1,u2)a vector defined onQ,{A(t), 0≤t≤+∞}is a family of operators inℒ(Hο1(Ω),H−1(Ω)), whereA(t)u=(A(t)u1,A(t)u2)andG:ℝ2→ℝ2a continuous function such thatx.G(x)≥0, forx∈ℝ2.Moreover, we obtain that the solutions of the above system with dissipative termu′have exponential decay.

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Hecker, Marcelle, Matthew Ting et Jenny Malmström. « Simple Coatings to Render Polystyrene Protein Resistant ». Coatings 8, n^o 2 (1 février 2018) : 55. http://dx.doi.org/10.3390/coatings8020055.

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Non-specific protein adsorption is detrimental to the performance of many biomedical devices. Polystyrene is a commonly used material in devices and thin films. Simple reliable surface modification of polystyrene to render it protein resistant is desired in particular for device fabrication and orthogonal functionalisation schemes. This report details modifications carried out on a polystyrene surface to prevent protein adsorption. The trialed surfaces included Pluronic F127 and PLL-g-PEG, adsorbed on polystyrene, using a polydopamine-assisted approach. Quartz crystal microbalance with dissipation (QCM-D) results showed only short-term anti-fouling success of the polystyrene surface modified with F127, and the subsequent failure of the polydopamine intermediary layer in improving its stability. In stark contrast, QCM-D analysis proved the success of the polydopamine assisted PLL-g-PEG coating in preventing bovine serum albumin adsorption. This modified surface is equally as protein-rejecting after 24 h in buffer, and thus a promising simple coating for long term protein rejection of polystyrene.

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Turov, V. V., V. M. Gun’ko, T. V. Krupskaya, I. S. Protsak, L. S. Andriyko, A. I. Marinin, A. P. Golovan, N. V. Yelagina et N. T. Kartel. « Interphase interactions of hydrophobic powders based on methilsilica in the water environment ». Surface 12(27) (30 décembre 2020) : 53–99. http://dx.doi.org/10.15407/surface.2020.12.053.

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Using modern physicochemical research methods and quantum chemical modeling, the surface structure, morphological and adsorption characteristics, phase transitions in heterogeneous systems based on methylsilica and its mixtures with hydrophilic silica were studied. It is established that at certain concentrations of interfacial water, hydrophobic silica or their composites with hydrophilic silica form thermodynamically unstable systems in which energy dissipation can be carried out under the influence of external factors: increasing water concentration, mechanical loads and adsorption of air by hydrophobic component. When comparing the binding energies of water in wet powders of wettind-drying samples A-300 and AM-1, which had close values of bulk density (1 g/cm3) and humidity (1 g/g), close to 8 J/g. However, the hydration process of hydrophobic silica is accompanied by a decrease in entropy and the transition of the adsorbent-water system to a thermodynamically nonequilibrium state, which is easily fixed on the dependences of interfacial energy (S) on the amount of water in the system (h). It turned out that for pure AM-1 the interfacial energy of water increases in proportion to its amount in the interparticle gaps only in the case when h < 1 g/g. With more water, the binding energy decreases abruptly, indicating the transition of the system to a more stable state, which is characterized by the consolidation of clusters of adsorbed water and even the formation of a bulk phase of water. Probably there is a partial "collapse" of the interparticle gaps of hydrophobic particles AM-1 and the release of thermodynamically excess water. For mixtures of hydrophobic and hydrophilic silica, the maximum binding of water is shifted towards greater hydration. At AM1/A-300 = 1/1 the maximum is observed at h = 3g/g, and in the case of AM1/A-300 = 1/2 it is not reached even at h = 4 g/g. The study of the rheological properties of composite systems has shown that under the action of mechanical loads, the viscosity of systems decreases by almost an order of magnitude. However, after withstanding the load and then reducing the load to zero, the viscosity of the system increases again and becomes significantly higher than at the beginning of the study. That is, the obtained materials have high thixotropic properties. Thus, a wet powder that has all the characteristics of a solid after a slight mechanical impact is easily converted into a concentrated suspension with obvious signs of liquid.

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Semaan, G., F. Ben Braham, M. Salhi et François Sanchez. « Roadmap to high-energy square pulses in anomalous dispersion fiber lasers ». Photonics Letters of Poland 8, n^o 4 (31 décembre 2016) : 95. http://dx.doi.org/10.4302/plp.2016.4.02.

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Dissipative soliton resonance (DSR) is a soliton formation where the energy in a dissipative system becomes infinite. In the anomalous dispersion regime, this energy is not limited by the soliton area theorem. Since this phenomenon is wave breaking free, it can be useful in designing fiber lasers generating pulses with relatively high energies. Based on this principle, we have demonstrated the emission of high energetic square pulses from Er:Yb double-clad passively mode-locked fiber lasers using different mode-locking mechanisms. We first show the evolution of pulse width, energy and peak power by varying the pumping power of the amplifier, then we control separately the characteristic of the output square pulse by assigning each one to an amplifier. Experimental results exhibit record energies in fiber lasers up to 10 uJ. Full Text: PDF ReferencesW. Chang, A. Ankiewicz, J.M Soto Crespo and N. Akhmediev, " Dissipative soliton resonances", Phys. Rev. A 78, 023830 (2008). CrossRef P. Grelu, W. Chang, A. Ankiewicz, J. M. Soto-Crespo, and N. Akhmediev, "Dissipative soliton resonance as a guideline for high-energy pulse laser oscillators", J. Opt. Soc. Am. B 27, 2336 (2010). CrossRef X. Wu, D. Y. Tang, H. Zhang, and L. M. Zhao, "Dissipative soliton resonance in an all-normal-dispersion erbium-doped fiber laser", Opt. Express 17, 5580 (2009). CrossRef G. Semaan, F. Ben Braham, M. Salhi, Y. Meng, F. Bahloul, and F. Sanchez, "Generation of high energy square-wave pulses in all anomalous dispersion Er:Yb passive mode locked fiber ring laser", Opt. Express 24, 8399 (2016). CrossRef K. Krzempek, "Dissipative soliton resonances in all-fiber Er-Yb double clad figure-8 laser", Opt. Express 23, 30651 (2015). CrossRef L. Mei et al., "Width and amplitude tunable square-wave pulse in dual-pump passively mode-locked fiber laser", Opt. Lett. 39, 3235 (2014). CrossRef X. Zhang et al., "Square-wave pulse with ultra-wide tuning range in a passively mode-locked fiber laser", Opt. Lett. 37, 1334 (2012). CrossRef K. Krzempek, J. Sotor, and K. Abramski, "Compact all-fiber figure-9 dissipative soliton resonance mode-locked double-clad Er:Yb laser", Opt. Lett. 41, 4995-4998 (2016). CrossRef G. Semaan, F. Ben Braham, J. Fourmont, M. Salhi, F. Bahloul, and F. Sanchez, "10uJ dissipative soliton resonance square pulse in a dual amplifier figure-of-eight double-clad Er:Yb mode-locked fiber laser", Opt. Lett. 41, 4767 (2016). CrossRef K. Krzempek and K. Abramski, "Dissipative soliton resonance mode-locked double clad Er:Yb laser at different values of anomalous dispersion", Opt. Express 24, 22379-22386 (2016). CrossRef

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Zhang, Y. C., Y. G. Xu, X. D. Chen et Y. F. Zhu. « Excitation Condition for Self-Sustained Oscillation in Flow Past a Louvered Cavity ». Journal of Mechanics 33, n^o 4 (6 juin 2017) : 535–44. http://dx.doi.org/10.1017/jmech.2017.43.

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AbstractLouvered cavities are extensively employed in engineering applications. In the configurations of flow past these cavities, self-sustained oscillations will be excited. This can give rise to structure vibrations or noise. Numerical models are established to analyze excitation condition for of these oscillations. Computational results reveal that the excitation condition can be quantitatively described by the ratio of gap width G to the boundary layer thickness δ at the separation edge. When G/δ exceeds a certain critical value G/δc, self-sustained oscillations are excited. Otherwise, disturbances will dissipate and the flow configuration along the louver will be like a parallel plate flow. The critical value G/δc decreases with the ratio of G to the thickness of the louver plate H. This suggests that the excitation condition is more easily satisfied for a louver with sparse fins. The bottom boundary of the cavity restricts the feedback flow and then suppresses the excitation of self-sustained oscillations. With an increasing cavity height Hc, which reflects the distance between the louver and the bottom boundary, the critical value G/δc decreases and the decreasing rate reduces gradually. In contrast, because G/δc is relatively insensitive to the cavity length Lc, the side boundaries have no obvious influence on the excitation condition.

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Arase, K., N. S. Shargill et G. A. Bray. « Effects of intraventricular infusion of corticotropin-releasing factor on VMH-lesioned obese rats ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 256, n^o 3 (1 mars 1989) : R751—R756. http://dx.doi.org/10.1152/ajpregu.1989.256.3.r751.

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Corticotropin-releasing factor (CRF) has been administered into the third ventricle of sham-operated and ventromedial hypothalamic (VMH)-lesioned rats in acute and chronic experiments. After a single 5-microgram injection of CRF, there was an acute reduction of food intake in both sham-operated and VMH-lesioned rats that persisted for 3 h. The effect was still present in the VMH-lesioned rats between 3 and 6 h but had dissipated in the sham-operated controls. Guanosine 5'-diphosphate (GDP) binding to mitochondria from interscapular brown adipose tissue was used as an index of thermogenic activity in this tissue. In 21-h food-deprived rats, GDP binding was significantly lower in VMH-lesioned than in sham-operated animals. Although the mean increase in sham-operated animals was increased, this was not significantly different from saline-injected controls. In the VMH-lesioned rats, however, CRF acutely increased GDP binding to values not different than those of the sham-operated controls. Serum corticosterone was significantly lower in the VMH-lesioned rats, but both groups showed a significant stimulation by CRF during a 7-day infusion of CRF (4.8 micrograms/day) into the third ventricle. Food intake was significantly depressed in the VMH-lesioned animals that received CRF, from values of 35 g/day to approximately 25 g/day. Body weight showed a slow steady decrease, having fallen by nearly 15 g at the end of the 7-day infusion period. In contrast the mean value in the VMH-lesioned controls had significantly higher in CRF-infused animals.(ABSTRACT TRUNCATED AT 250 WORDS)

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Toledo, Felipe, Martial Haeffelin, Eivind Wærsted et Jean-Charles Dupont. « A new conceptual model for adiabatic fog ». Atmospheric Chemistry and Physics 21, n^o 17 (3 septembre 2021) : 13099–117. http://dx.doi.org/10.5194/acp-21-13099-2021.

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Abstract. Visibility reduction caused by fog can be hazardous for human activities, especially for the transport sector. Previous studies show that this problem could be mitigated by improving nowcasting of fog dissipation. To address this issue, we propose a new paradigm which could potentially improve our understanding of the life cycle of adiabatic continental fogs and of the conditions that must take place for fog dissipation. For this purpose, adiabatic fog is defined as a layer filled with suspended liquid water droplets, extending from an upper boundary all the way down to the surface, with a saturated adiabatic temperature profile. In this layer, the liquid water path (LWP) must exceed a critical value: the critical liquid water path (CLWP). When the LWP is less than the CLWP, the amount of fog liquid water is not sufficient to extend all the way down to the surface, leading to a surface horizontal visibility greater than 1 km. Conversely, when the LWP exceeds the CLWP, the amount of cloud water is enough to reach the surface, inducing a horizontal visibility of less than 1 km. The excess water with respect to the critical value is defined as the reservoir liquid water path (RLWP). The new fog paradigm is formulated as a conceptual model that relates the liquid water path of adiabatic fog with its thickness and surface liquid water content and allows the critical and reservoir liquid water paths to be computed. Both variables can be tracked in real time using vertical profiling measurements, enabling a real-time diagnostic of fog status. The conceptual model is tested using data from 7 years of measurements performed at the SIRTA observatory, combining cloud radar, microwave radiometer, ceilometer, scatterometer, and weather station measurements. In this time period we found 80 fog events with reliable measurements, with 56 of these lasting more than 3 h. The paper presents the conceptual model and its capability to derive the LWP from the fog top height and surface horizontal visibility with an uncertainty of 10.5 g m−2. The impact of fog liquid water path and fog top height variations on fog life cycle (formation to dissipation) is presented based on four case studies and statistics derived from 56 fog events. Our results, based on measurements and an empirical parametrization for the adiabaticity, validate the applicability of the model. The calculated reservoir liquid water path is consistently positive during the mature phase of fog and starts to decrease quasi-monotonously about 1 h before dissipation, reaching a near-zero value at the time of dissipation. Hence, the reservoir liquid water path and its time derivative could be used as indicators of the life cycle stage, to support nowcasting of fog dissipation.

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A. Fetoh, Badr El-Sabah, Mahmoud M. Ramadan et Abdelhadi A. I. Ali. « Chlorfenapyr and Methomyl Deterioration on Spinach Plants and Their Residual Effects in Vitro on Egyptian cotton Leafworm (Spodoptera littoralis) ». Nutrition and Food Processing 4, n^o 7 (13 novembre 2021) : 01–08. http://dx.doi.org/10.31579/2637-8914/068.

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Field trials conducted to determine the degradation of chlorfenapyr and methomyl insecticides in/on spinach leaves. Spinach plants sprayed with chlorfenapyr (Challenger Super™ 24% SC) and methomyl (Neomyl™ 90% SP) at the rates of 50 cm3/100 L water and 715 g/ ha, respectively. The QuEChERS method used for the extraction and clean-up of the samples. Residue amounts determined at 2 h, 2, 4, 6, 9, 13 and 16 days after application by UHPLC-UV. The mean of recovery percentages was 98.78 and 99.05 % for chlorfenapyr and methomyl, respectively. The initial deposits of chlorfenapyr and methomyl on/in spinach leaves, two hours after a single application of the insecticides were 23.17 and 235.37 mg/kg, respectively. The percentages of dissipation of chlorfenapyr were 37.68, 55.29, 69.45, 84.45 and 96.83% for 2, 4, 6, 9 and 16 days after application. The corresponding dissipation percentages of methomyl were 38.27, 56.01, 71.44, 84.34 and 97.81%. The rates of degradation (k values) were 0.212 and 0.223, while the corresponding half-life times (t0.5) were 3.27 and 3.11 days with chlorfenapyr and methomyl, respectively. It could be recommended that single application of chlorfenapyr on Spinach plants at the early ages followed by single application of methomyl at least 17 days before harvest.

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Phetkhajone, Supawadee, Aussanee Pichakum et Wisuwat Songnuan. « The Study of the Kinetics of Metalaxyl Accumulation and Dissipation in Durian (Durio zibethinus L.) Leaf Using High-Performance Liquid Chromatography (HPLC) Technique ». Plants 10, n^o 4 (6 avril 2021) : 708. http://dx.doi.org/10.3390/plants10040708.

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Metalaxyl is an effective approach to control Phytophthora palmivora infection in durian plantation. However, inappropriate metalaxyl usage may increase production cost, pathogen with fungicide resistance, and environmental toxicity. This study established and validated a simple and reproducible procedure to measure metalaxyl concentration in the durian leaf using HPLC. Linearity of the detection ranged from 1–100 µg/mL. The limits of detection (LOD) and quantification (LOQ) were 0.27 and 0.91 µg/mL, respectively. The extraction method gave recovery rates ranging from 88% to 103%. Durian seedlings were treated with 4 g/L metalaxyl either by foliar spray or soil drench. The highest metalaxyl accumulation in durian leaf was found between 6–24 h after treatment and persisted above its effective concentration at least 60 days after foliar application. The dissipation pattern fit to a first-order kinetics equation showed a half-life of 16.50 days. Soil drenching led to eight times higher metalaxyl concentrations in plants than foliar spraying and caused plant death within 15 days after application. These results suggest that foliar spraying of 4 g/L metalaxyl or soil drenching at a lower concentration every two months is sufficient in controlling P. palmivora infection in durian seedlings.

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Lim, Ji Hye, Mi Mi Ko, Hoyoung Lee, Ho Yeon Go, Tae-Woong Moon, Min Ho Cha et Myeong Soo Lee. « Differential Association of Uncoupling Protein 2 Polymorphisms with Pattern Identification among Korean Stroke Patients : A Diagnostic System in Traditional Korean Medicine ». Evidence-Based Complementary and Alternative Medicine 2012 (2012) : 1–9. http://dx.doi.org/10.1155/2012/532078.

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Uncoupling protein 2 (UCP2), a mitochondrial protein present in many organs and cell types, is known to dissipate the proton gradient formed by the electron transport chain. Its function is correlated with predictive parameters, such as obesity, diabetes, and metabolic syndromes. We analyzed the distribution of UCP2 polymorphisms in stroke patients diagnosed with one of the following four stroke subtypes based on the TKM standard pattern identification (PI): Qi-deficiency (QD), Dampness and Phlegm (D&P), Yin-deficiency (YD), and Fire and Heat (F&D). We studied a total of 1,786 stroke patients (397/QD, 645/D&P, 223/YD, and 522/F&D, 586/normal). Genotyping for the G-1957A, G-866A and A55V UCP2 polymorphisms was performed using the TaqMan. G-866A and A55V were significantly associated with the D&P and H&F subtypes. The frequency of subjects with the A allele of G-866A was significantly lower than the frequency of subjects with the GG type. The A55V polymorphism was also shown similar effect with G-866A in the dominant model. In contrast, no SNPs were shown to be associated with the QD or YD subtypes in this study. These results showed that the G-866A and A55V UCP2 polymorphisms may be genetic factors for specific PI types among Korean stroke patients.

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Malairuang, Kwanruthai, Morakot Krajang, Jatuporn Sukna, Krongchan Rattanapradit et Saethawat Chamsart. « High Cell Density Cultivation of Saccharomyces cerevisiae with Intensive Multiple Sequential Batches Together with a Novel Technique of Fed-Batch at Cell Level (FBC) ». Processes 8, n^o 10 (21 octobre 2020) : 1321. http://dx.doi.org/10.3390/pr8101321.

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High cell density cultivation (HCDC) is developed for the production of microbial biomasses and their products. They must be produced from high concentrations of substrate, e.g., glucose or sucrose. In batch culture, a high concentration of those sugars >40–50% (w/v) cannot efficiently be utilized because of a dissolved O2 limitation causing the Crabtree effect that produces toxic by-products, i.e., ethanol and/or acetate, that inhibit cell growth. To prevent this effect, the HCDC is conducted with the fed-batch strategies. However, it has many disadvantages, i.e., complicated operations. To overcome those problems, this study was designed to use a new, efficient C-source (carbon source) substrate, namely dextrin, an oligomer of glucose. It can be utilized by yeast at a very high concentration of ~100 g/L although using just batch cultivation. As it is gradually hydrolyzed to release glucose molecules and gradually assimilated into the cells as “fed-batch at the cell level” (FBC), it prevents the yeast cell system from undergoing the Crabtree effect. In this research, the types of medium, the types of sugar compared with dextrin, and the concentrations of yeast extract (YE) were studied. The batch production medium (BPM) with dextrin and YE performed very good results. The concentrations of dextrin for yeast cultivation were studied in the aerobic batch 5-L bioreactors. Its optimum concentration was at 90 g/L with 9 g/L of YE in 3× BPM. It was operated at 3 W/kg energy dissipation rate per unit mass (ε¯T) and 3 vvm airflow rate. Further, the intensive multiple sequential batch (IMSB) technique of high intensities of agitation speed and airflow was developed to achieve higher yield and productivity. The maximum values of cell biomass, specific growth rate, yield coefficient, productivity, and efficiency were at 55.17 g/L, 0.21 h−1, 0.54 g/g, 2.30 g/L/h, and 98.18%, respectively. The studies of cell growth kinetics, biochemical engineering mass balances, and fluid dynamics for the design of impeller speeds of the 5-L bioreactors during the cultivations of yeast using dextrin at the high concentrations were successful. The results can be used for the scale-up of bioreactor for the industrial production of yeast cell biomass at high concentrations.

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Li, Hai Ling, Jun Suzuki, Evelyn Bayna, Fu-Min Zhang, Erminia Dalle Molle, Aaron Clark, Robert L. Engler et Wilbur Y. W. Lew. « Lipopolysaccharide induces apoptosis in adult rat ventricular myocytes via cardiac AT1 receptors ». American Journal of Physiology-Heart and Circulatory Physiology 283, n^o 2 (1 août 2002) : H461—H467. http://dx.doi.org/10.1152/ajpheart.00701.2001.

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Lipopolysaccharide (LPS) from gram-negative bacteria circulates in acute, subacute, and chronic conditions. It was hypothesized that LPS directly induces cardiac apoptosis. In adult rat ventricular myocytes (isolated with depyrogenated digestive enzymes to minimize tolerance), LPS (10 ng/ml) decreased the ratio of Bcl-2 to Bax at 12 h; increased caspase-3 activity at 16 h; and increased annexin V, propidium iodide, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining at 24 h. Apoptosis was blocked by the caspase inhibitor benzyloxycarbonyl-valine-alanine-aspartate fluoromethylketone (Z-VAD-fmk), captopril, and angiotensin II type 1 receptor (AT1) inhibitor (losartan), but not by inhibitors of AT2 receptors (PD-123319), tumor necrosis factor-α (TNFRII:Fc), or nitric oxide ( N G-monomethyl-l-arginine). Angiotensin II (100 nmol/l) induced apoptosis similar to LPS without additive effects. LPS in vivo (1 mg/kg iv) increased apoptosis in left ventricular myocytes for 1–3 days, which dissipated after 1–2 wk. Losartan (23 mg · kg−1 · day−1 in drinking water for 3 days) blocked LPS-induced in vivo apoptosis. In conclusion, low levels of LPS induce cardiac apoptosis in vitro and in vivo by activating AT1 receptors in myocytes.

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Hannan, Md Abdul, Md Nazmul Haque, Md Mohibbullah, Raju Dash, Yong-Ki Hong et Il Soo Moon. « Gelidium amansii Attenuates Hypoxia/Reoxygenation-Induced Oxidative Injury in Primary Hippocampal Neurons through Suppressing GluN2B Expression ». Antioxidants 9, n^o 3 (9 mars 2020) : 223. http://dx.doi.org/10.3390/antiox9030223.

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Oxidative stress is known to be critically implicated in the pathophysiology of several neurological disorders, including Alzheimer’s disease and ischemic stroke. The remarkable neurotrophic activity of Gelidium amansii, which has been reported consistently in a series of our previous studies, inspired us to investigate whether this popular agarophyte could protect against hypoxia/reoxygenation (H/R)-induced oxidative injury in hippocampal neurons. The primary culture of hippocampal neurons challenged with H/R suffered from a significant loss of cell survival, accompanied by apoptosis and necrosis, DNA damage, generation of reactive oxygen species (ROS), and dissipation of mitochondrial membrane potential (ΔΨm), which were successfully attenuated when the neuronal cultures were preconditioned with ethanolic extract of G. amansii (GAE). GAE also attenuated an H/R-mediated increase of BAX and caspase 3 expressions while promoting Bcl-2 expression. Moreover, the expression of N-methyl-d-acetate receptor subunit 2B (GluN2B), an extrasynaptic glutamate receptor, was significantly repressed, while synaptic GluN2A expression was preserved in GAE-treated neurons as compared to those without GAE intervention. Together, this study demonstrates that GAE attenuated H/R-induced oxidative injury in hippocampal neurons through, at least in part, a potential neuroprotective mechanism that involves inhibition of GluN2B-mediated excitotoxicity and suppression of ROS production, and suggests that this edible seaweed could be a potential source of bioactive metabolites with therapeutic significance against oxidative stress-related neurodegeneration, including ischemic stroke and neurodegenerative diseases.

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Kareem, Aseel A. « Enhanced thermal and electrical properties of epoxy/carbon fiber–silicon carbide composites ». Advanced Composites Letters 29 (1 janvier 2020) : 2633366X1989459. http://dx.doi.org/10.1177/2633366x19894598.

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The silicon carbide/carbon fiber (SiC/CF) hybrid fillers were introduced to improve the electrical and thermal conductivities of the epoxy resin composites. Results of Fourier transform infrared spectroscopy revealed that the peaks at 3532 and 2850 cm−1 relate to carboxylic acid O–H stretching and aldehyde C–H stretching appearing deeper with an increased volume fraction of SiC. Scanning electron microscopic image shows a better interface bonding between the fiber and the matrix when the volume fraction of SiC particles are increased. As frequency increases from 102 Hz to 106 Hz, dielectric constants decrease slightly. Dissipation factor (tan δ) values keep low and almost constant from 102 Hz to 104 Hz, has a slight increase after 104 Hz, and obtain relaxation peaks approximately between 105 and 106 Hz. A sharp increase in dielectric constant and dissipation factors is observed in epoxy (Ep)/CF composites with 30 vol.% of SiC. The increase in electrical conductivity of composites may result from the increased chain ordering by annealing effect. The electrical conductivities of the Ep/CF composites are decreasing with the increasing volume fraction of SiC. It is attributed to the introduction of insulating SiC. The glass transition temperature ( T g) of the Ep/CF-30 vol.% SiC composite was 352 C, which was higher than other composites. The decomposition temperature at 5% weight loss, decomposition temperature at 10% weight loss, and maximum decomposition temperature of the Ep/CF-30 vol.% SiC composite were about 389.5°C, 410.7°C, and 591°C, respectively, and were higher than pure epoxy and other composites. A higher thermal conductivity of 1.86 W (m K)−1 could be achieved with 30 vol.% SiC/CF hybrid fillers, which is about nine times higher than that of native epoxy resin of 0.202 W (m.K)−1.

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Pijls, B. G., I. M. J. G. Sanders, E. J. Kuijper et R. G. H. H. Nelissen. « Segmental induction heating of orthopaedic metal implants ». Bone & ; Joint Research 7, n^o 11 (novembre 2018) : 609–19. http://dx.doi.org/10.1302/2046-3758.711.bjr-2018-0080.r1.

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Objectives Prosthetic joint infection (PJI) is a devastating complication following total joint arthroplasty. Non-contact induction heating of metal implants is a new and emerging treatment for PJI. However, there may be concerns for potential tissue necrosis. It is thought that segmental induction heating can be used to control the thermal dose and to limit collateral thermal injury to the bone and surrounding tissues. The purpose of this study was to determine the thermal dose, for commonly used metal implants in orthopaedic surgery, at various distances from the heating centre (HC). Methods Commonly used metal orthopaedic implants (hip stem, intramedullary nail, and locking compression plate (LCP)) were heated segmentally using an induction heater. The thermal dose was expressed in cumulative equivalent minutes at 43°C (CEM43) and measured with a thermal camera at several different distances from the HC. A value of 16 CEM43 was used as the threshold for thermal damage in bone. Results Despite high thermal doses at the HC (7161 CEM43 to 66 640 CEM43), the thermal dose at various distances from the HC was lower than 16 CEM43 for the hip stem and nail. For the fracture plate without corresponding metal screws, doses higher than 16 CEM43 were measured up to 5 mm from the HC. Conclusion Segmental induction heating concentrates the thermal dose at the targeted metal implant areas and minimizes collateral thermal injury by using the non-heated metal as a heat sink. Implant type and geometry are important factors to consider, as they influence dissipation of heat and associated collateral thermal injury. Cite this article: B. G. Pijls, I. M. J. G. Sanders, E. J. Kuijper, R. G. H. H. Nelissen. Segmental induction heating of orthopaedic metal implants. Bone Joint Res 2018;7:609–619. DOI: 10.1302/2046-3758.711.BJR-2018-0080.R1.

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Pham, Huy Thang, Key Zoung Riu, Kong Man Jang, Somi K. Cho et Moonjae Cho. « Bactericidal Activity of Glycinecin A, a Bacteriocin Derived from Xanthomonas campestris pv. glycines, on Phytopathogenic Xanthomonas campestris pv. vesicatoria Cells ». Applied and Environmental Microbiology 70, n^o 8 (août 2004) : 4486–90. http://dx.doi.org/10.1128/aem.70.8.4486-4490.2004.

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ABSTRACT The ability of glycinecin A, a bacteriocin derived from Xanthomonas campestris pv. glycines 8ra, to kill closely related bacteria has been demonstrated previously by our group (S. G. Heu et al., Appl. Environ. Microbiol. 67:4105-4110, 2001). In the present study, we aimed at determining the glycinecin A-induced cause of death. Treatment with glycinecin A caused slow dissipation of membrane potential and rapid depletion of the pH gradient. Glycinecin A treatment also induced leakage of potassium ions from X. campestris pv. vesicatoria YK93-4 cells and killed sensitive bacterial cells in a dose-dependent manner. Sensitive cells were killed within 2 h of incubation, most likely due to the potassium ion efflux caused by glycinecin A. These results suggest that the bactericidal mechanism of action of glycinecin A is correlated with the permeability of membranes to hydroxyl and potassium ions, leading to the lethal activity of the bacteriocin on the target bacteria.

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Meneses-Brassea, Bianca P., Edgar A. Borrego, Dawn S. Blazer, Mohamed F. Sanad, Shirin Pourmiri, Denisse A. Gutierrez, Armando Varela-Ramirez, George C. Hadjipanayis et Ahmed A. El-Gendy. « Ni-Cu Nanoparticles and Their Feasibility for Magnetic Hyperthermia ». Nanomaterials 10, n^o 10 (9 octobre 2020) : 1988. http://dx.doi.org/10.3390/nano10101988.

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Ni-Cu nanoparticles have been synthesized by reducing Ni and Cu from metal precursors using a sol–gel route followed by annealing at 300 °C for 1, 2, 3, 6, 8, and 10 h for controlled self-regulating magnetic hyperthermia applications. Particle morphology and crystal structure revealed spherical nanoparticles with a cubic structure and an average size of 50, 60, 53, 87, and 87 nm for as-made and annealed samples at 300 °C for 1, 3, 6, and 10 h, respectively. Moreover, hysteresis loops indicated ferromagnetic behavior with saturation magnetization (Ms) ranging from 13–20 emu/g at 300 K. Additionally, Zero-filed cooled and field cooled (ZFC-FC) curves revealed that each sample contains superparamagnetic nanoparticles with a blocking temperature (TB) of 196–260 K. Their potential use for magnetic hyperthermia was tested under the therapeutic limits of an alternating magnetic field. The samples exhibited a heating rate ranging from 0.1 to 1.7 °C/min and a significant dissipated heating power measured as a specific absorption rate (SAR) of 6–80 W/g. The heating curves saturated after reaching the Curie temperature (Tc), ranging from 30–61 °C within the therapeutic temperature limit. An in vitro cytotoxicity test of these Ni-Cu samples in biological tissues was performed via exposing human breast cancer MDA-MB231 cells to a gradient of concentrations of the sample with 53 nm particles (annealed at 300 °C for 3 h) and reviewing their cytotoxic effects. For low concentrations, this sample showed no toxic effects to the cells, revealing its biocompatibility to be used in the future for in vitro/in vivo magnetic hyperthermia treatment of cancer.

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Qu, Daofeng, Mengxue Jiang, Dongping Huang, Hui Zhang, Lifang Feng, Yuewen Chen, Xuan Zhu, Suhua Wang et Jianzhong Han. « Synergistic Effects of The Enhancements to Mitochondrial ROS, p53 Activation and Apoptosis Generated by Aspartame and Potassium Sorbate in HepG2 Cells ». Molecules 24, n^o 3 (28 janvier 2019) : 457. http://dx.doi.org/10.3390/molecules24030457.

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The safety of food additives has been widely concerned. Using single additives in the provisions of scope is safe, but the combination of additives, may induce additive, synergy, antagonism and other joint effects. This study investigated the cytotoxicity of aspartame (AT) together with potassium sorbate (PS). Thiazolyl Blue Tetrazolium Bromide (MTT) assay indicated that AT and PS had IC50 values of 0.48 g/L and 1.25 g/L at 24 h, respectively. High content analysis (HCA) showed that both AT and PS had a negative effect on mitochondrial membrane potential (MMP), reactive oxygen species (ROS) and DNA damage while the joint group behaved more obviously. The biochemical assays revealed typical cell morphological changes and the activation of cytochrome c and caspase-3 verified apoptosis induced by AT together with PS. With dissipation of MMP and increase of cell membrane permeability (CMP), it indicated AT together with PS-induced apoptosis was mediated by mitochondrial pathway. Meanwhile, p53 were involved in DNA damage, and the ratio of Bax/Bcl-2 was increased. Moreover, excessive ROS induced by AT together with PS is a key initiating factor for apoptosis. All these results proved that p53 was involved in apoptosis via mitochondria-mediated pathway and the process was regulated by ROS.

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Urthaler, Ferdinand, Alfred A. Walker, Russell C. Reeves et Lloyd L. Hefner. « Excitation–contraction coupling model to estimate the recirculating fraction of activator calcium in intact cardiac muscle ». Canadian Journal of Physiology and Pharmacology 68, n^o 8 (1 août 1990) : 1041–48. http://dx.doi.org/10.1139/y90-157.

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Potentiated contractions were evoked with a rapid pace pause maneuver in 14 length-clamped ferret papillary muscles paced 12 times/min at 25 °C. At 1.25 mM [Ca2+]o the average steady-state force was 2.94 ± 1.08 g/mm2 and the potentiated contraction averaged 10.96 ± 1.61 g/mm2. At 5.0 mM [Ca2+]o the steady-state force increased to 6.18 ± 1.23 g/mm2 and the potentiated contraction averaged 12.08 ± 1.15 g/mm2. Under the conditions of these experiments the potentiated contraction obtained at 5.0 mM [Ca2+]o is equal to the maximum twitch tension (Fmax) these muscles can generate. We have previously shown that Fmax is an equivalent of maximal calcium activated force. Since there is a beat to beat nearly exponential decay of the evoked potentiation, the fraction (= fraction x) of the potentiation that is not dissipated with each beat is nearly constant. Using an excitation–contraction coupling model we have previously found that x reflects a measure of the recirculating fraction of activator calcium. Because the tension–calcium relationship is better characterized by a sigmoidal curve, we have now incorporated the Hill equation in the model. To account for the inverse relationship between [Ca2+]i and the magnitude of the slow inward current, a term for negative feedback (h) was also included. We have determined the quantity (x – h) because x and h could not be determined separately. The quantity (x – h) was denoted as x′. The average values of x′ at 1.25 and 5.0 mM [Ca2+]o were significantly different (p < 0.0001), approximately 20% at the lower [Ca2+]o and about 50% at the higher [Ca2+]o. An attempt to estimate both x′ and the Hill coefficient N simultaneously has shown that the determination of N must be considered inaccurate, but even larger variations of N have little influence on x′. Thus, in intact ferret ventricular muscle, the model predicts that at 1.25 mM [Ca2+]o only about 20% of the activator calcium recirculates, while some 80% comes across the sarcolemma from the extracellular compartment. The model also predicts that the recirculating fraction doubles when [Ca2+]o is elevated to 5 mM.Key words: length-clamped papillary muscle, maximum twitch tension, excitation–contraction coupling model, recirculating fraction of activator calcium, transsarcolemmal fraction of activator calcium.

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Zhou, Qi, John R. Taylor et C. P. Caulfield. « Self-similar mixing in stratified plane Couette flow for varying Prandtl number ». Journal of Fluid Mechanics 820 (4 mai 2017) : 86–120. http://dx.doi.org/10.1017/jfm.2017.200.

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We investigate fully developed turbulence in stratified plane Couette flows using direct numerical simulations similar to those reported by Deusebioet al.(J. Fluid Mech., vol. 781, 2015, pp. 298–329) expanding the range of Prandtl number$Pr$examined by two orders of magnitude from 0.7 up to 70. Significant effects of$Pr$on the heat and momentum fluxes across the channel gap and on the mean temperature and velocity profile are observed. These effects can be described through a mixing length model coupling Monin–Obukhov (M–O) similarity theory and van Driest damping functions. We then employ M–O theory to formulate similarity scalings for various flow diagnostics for the stratified turbulence in the gap interior. The midchannel gap gradient Richardson number$Ri_{g}$is determined by the length scale ratio$h/L$, where$h$is the half-channel gap depth and$L$is the Obukhov length scale. As$h/L$approaches very large values,$Ri_{g}$asymptotes to a maximum characteristic value of approximately 0.2. The buoyancy Reynolds number$Re_{b}\equiv \unicode[STIX]{x1D700}/(\unicode[STIX]{x1D708}N^{2})$, where$\unicode[STIX]{x1D700}$is the dissipation,$\unicode[STIX]{x1D708}$is the kinematic viscosity and$N$is the buoyancy frequency defined in terms of the local mean density gradient, scales linearly with the length scale ratio$L^{+}\equiv L/\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}}$, where$\unicode[STIX]{x1D6FF}_{\unicode[STIX]{x1D708}}$is the near-wall viscous scale. The flux Richardson number$Ri_{f}\equiv -B/P$, where$B$is the buoyancy flux and$P$is the shear production, is found to be proportional to$Ri_{g}$. This then leads to a turbulent Prandtl number$Pr_{t}\equiv \unicode[STIX]{x1D708}_{t}/\unicode[STIX]{x1D705}_{t}$of order unity, where$\unicode[STIX]{x1D708}_{t}$and$\unicode[STIX]{x1D705}_{t}$are the turbulent viscosity and diffusivity respectively, which is consistent with Reynolds analogy. The turbulent Froude number$Fr_{h}\equiv \unicode[STIX]{x1D700}/(NU^{\prime 2})$, where$U^{\prime }$is a turbulent horizontal velocity scale, is found to vary like$Ri_{g}^{-1/2}$. All these scalings are consistent with our numerical data and appear to be independent of$Pr$. The classical Osborn model based on turbulent kinetic energy balance in statistically stationary stratified sheared turbulence (Osborn,J. Phys. Oceanogr., vol. 10, 1980, pp. 83–89), together with M–O scalings, results in a parameterization of$\unicode[STIX]{x1D705}_{t}/\unicode[STIX]{x1D708}\sim \unicode[STIX]{x1D708}_{t}/\unicode[STIX]{x1D708}\sim Re_{b}Ri_{g}/(1-Ri_{g})$. With this parameterization validated through direct numerical simulation data, we provide physical interpretations of these results in the context of M–O similarity theory. These results are also discussed and rationalized with respect to other parameterizations in the literature. This paper demonstrates the role of M–O similarity in setting the mixing efficiency of equilibrated constant-flux layers, and the effects of Prandtl number on mixing in wall-bounded stratified turbulent flows.

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