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We present a numerical analysis of the rheology of a suspension of red blood cells (RBCs) for different volume fractions in a wall-bounded, effectively inertialess, small amplitude oscillatory shear (SAOS) flow for a wide range of applied frequencies. The RBCs are modeled as biconcave capsules, whose membrane is an isotropic and hyperelastic material following the Skalak constitutive law. The frequency-dependent viscoelasticity in the bulk suspension is quantified by the complex viscosity, defined by the amplitude of the particle shear stress and the phase difference between the stress and shear. SAOS flow basically impedes the deformation of individual RBCs as well as the magnitude of fluid-membrane interactions, resulting in a lower specific viscosity and first and second normal stress differences than in steady shear flow. Although it is known that the RBC deformation alone is sufficient to give rise to shear-thinning, our results show that the complex viscosity weakly depends on the frequency-modulated deformations or orientations of individual RBCs but rather depends on combinations of the frequency-dependent amplitude and phase difference. The effect of the viscosity ratio between the cytoplasm and plasma and of the capillary number is also assessed. [ABSTRACT FROM AUTHOR]

The rate of change ε ( k , t ) = ∂ E ( k , t ) ∕ ∂ t of the energy spectrum E ( k , t ) of a weak turbulence in a system with a decay dispersion relation is investigated with particular interests in the initial stage of evolution such as the first several tens of periods. The theoretical predictions given by the kinetic equation of Hasselmann and that of Janssen which have been derived by the weak turbulence theory are compared with the results of direct numerical simulation (DNS) with a great accuracy. It is shown that ε ( k , t ) predicted by Janssen’s equation correctly reproduces the rapid variation of ε ( k , t ) with the linear time-scale which is observed in DNS, while that predicted by Hasselmann’s equation does not. It is also shown that the transient behavior of the asymptotic approach of Janssen’s ε ( k , t ) to Hasselmann’s one strongly depends on the wavenumber. For wavenumbers smaller than the spectral peak, the approach is exponential, while for wavenumbers larger than the spectral peak it contains a damped oscillation whose amplitude decays in time like 1 ∕ t . A reasonable explanation for the origin of this damped oscillation is given in terms of the frequency mismatch of the three-wave “sum” interactions. [ABSTRACT FROM AUTHOR]

A weakly nonlinear spectrum and a strongly nonlinear spectrum coexist in a statistically steady state of elastic wave turbulence. The analytical representation of the nonlinear frequency is obtained by evaluating the extended self-nonlinear interactions. The critical wave numbers at which the nonlinear frequencies are comparable with the linear frequencies agree with the separation wave numbers between the weak and strong turbulence spectra. We also confirm the validity of our analytical representation of the separation wave numbers through comparison with the results of direct numerical simulations by changing the material parameters of a vibrating plate. [ABSTRACT FROM AUTHOR]

The random-phase-and-amplitude-formalism (RPA) has significantly extended the scope of weak turbulence studies. Because the RPA does not assume any proximity to the Gaussianity in the wave number space, it can predict, for example, how the fluctuation of the complex amplitude of each wave mode grows through nonlinear interactions with other modes and how it approaches the Gaussianity. Thus, the RPA has a great potential capability, but its validity has been assessed neither numerically nor experimentally. We compare the theoretical predictions given by the RPA with the results of direct numerical simulations (DNS) for a three-wave Hamiltonian system, thereby assessing the validity of the RPA. The predictions of the RPA agree quite well with the results of DNS in all the aspects of the statistical characteristics of the mode amplitudes studied here. [ABSTRACT FROM AUTHOR]

A variety of statistically steady energy spectra in elastic wave turbulence have been reported in numerical simulations, experiments, and theoretical studies. Focusing on the energy levels of the system, we perform direct numerical simulations according to the Föppl-von Kármán equation, and successfully reproduce the variability of the energy spectra by changing the magnitude of external force systematically. When the total energies in wave fields are small, the energy spectra are close to a statistically steady solution of the kinetic equation in the weak turbulence theory. On the other hand, in large-energy wave fields, another self-similar spectrum is found. The coexistence of the weakly nonlinear spectrum in large wave numbers and the strongly nonlinear spectrum in small wave numbers is also found in moderate energy wave fields. [ABSTRACT FROM AUTHOR]

Abstract: In wave turbulence, which is made by nonlinear interactions among waves, it has been believed that statistical properties are well described by the weak turbulence theory, where separation of linear and nonlinear time scales derived from weak nonlinearity is assumed. However, the separation of the time scales is often violated. To get rid of this inconsistency, closed equations are derived in wave turbulence without assuming the weak nonlinearity according to Direct-Interaction Approximation (DIA), which has been successful in Navier–Stokes turbulence. The DIA equations is a natural extension of the conventional kinetic equation to not-necessarily-weak wave turbulence. [Copyright &y& Elsevier]

Abstract: A series of numerical studies has been performed to investigate the statistical characteristics of fluctuations of energy of each component wave and its time derivative in a wave turbulence for a Hamiltonian system with a non-decay type dispersion relation. It has been found that the probability density functions (PDF) of and evaluated among independent realizations are almost equivalent to the PDF’s evaluated among nearby modes in the space in a single realization. Therefore, the averaging over the realizations and that over the nearby modes in a single realization are interchangeable. It has also been found that the PDF of evolves in time toward the distribution with two degrees of freedom, while that of evolves toward the Laplace distribution (or the two-sided exponential distribution) at any wavenumber , both in the peripheral of the spectrum (large region) and in the energy-containing range (small region). [Copyright &y& Elsevier]

Abstract: To investigate the formation mechanism of energy spectra of internal waves in the oceans, direct numerical simulations are performed. The simulations are based on the reduced dynamical equations of rotating stratified turbulence. In the reduced dynamical equations only wave modes are retained, and vortices and horizontally uniform vertical shears are excluded. Despite the simplifications, our simulations reproduce some key features of oceanic internal-wave spectra: accumulation of energy at near-inertial waves and realistic frequency and horizontal wavenumber dependencies. Furthermore, we provide evidence that formation of the energy spectra in the inertial subrange is dominated by scale-separated interactions with the near-inertial waves. These findings support observationally based intuition that spectral energy density of internal waves is the result of predominantly wave–wave interactions. [Copyright &y& Elsevier]

[Display omitted] • Cerebrospinal fluid flow is driven by the arterial pulsation. • Net flow velocity in numerical simulations agrees with that in animal experiments. • The net flow velocity is theoretically given by the lubrication theory in analogy with Taylor's swimming sheet model. • Lubrication theory rationalizes the net flow veolocity. The lubrication theory used is analogous to Taylor's swimming sheet model. Cerebrospinal fluid (CSF) flow in the perivascular space (PVS), which surrounds the arteries in the brain, is of paramount importance in the removal of metabolic waste. Despite a number of experimental and numerical studies regarding CSF flow, the underlying mechanics of CSF flow are still debated, especially regarding whether an arterial pulsation can indeed produce net CSF flow velocity. Furthermore, the relationship between CSF flow and arterial wall pulsation has not been fully defined. To clarify these questions, we numerically investigated the CSF flow in the PVS in an axisymmetric channel with a pulsating boundary, where CSF is modeled as an incompressible, Newtonian viscous fluid in non-porous space. Our numerical results show that the net CSF flow velocity driven by the arterial pulsation is consistent with that of previous animal experiments. However, the peak oscillatory velocity is two orders of magnitude larger than the net velocity. Interestingly, the net CSF flow velocity collapses on the analytical solution derived from the lubrication theory in analogy with Taylor's swimming sheet model. [ABSTRACT FROM AUTHOR]

This paper reports on the first gymnastic robot that can perform back handspring. The robot is a planar and serially connected four-link robot, with its joints actuated by electric servomotors. The paper describes the modeling of the robot and the control framework for a back handspring. The controller is derived from a task-specific reference model and its model matching. The use of a reference model described by global physical quantities such as center of mass or angular momentum allows the gymnastic motion planning of a multi-body system to be intuitive and the model matching controller can be applied directly to the experimental model without obtaining each joint trajectory. The controller effectiveness is confirmed via simulations and experiments of the back handspring. Although there remains the problem of how to systematically design the control parameters, the paper shows the strength of the model-based controller for fast gymnastic motions. [ABSTRACT FROM AUTHOR]

The effects of discretization of the spectrum on the evolution of weak turbulence of surface gravity waves are investigated by direct numerical simulations. Discretization of the spectrum is implemented by imposing periodic boundary conditions on the horizontal plane. Initial wave fields are constructed so that they have the JONSWAP spectrum, and the nonlinear energy transfer among component waves is estimated by following their evolution deterministically according to the primitive governing equations. It is found that the discretized system can produce the same nonlinear energy transfer as that predicted theoretically for a continuous spectrum, even when the distribution of component waves on the wavenumber plane is so sparse that the corresponding area of the water surface on the horizontal plane is just 4λp×4λp, with λp being the wavelength corresponding to the peak of the spectrum, provided that the ensemble averaging is taken over a sufficient number of realizations. The regime of “frozen” turbulence, which is known to appear in the weak turbulence of capillary waves with a discretized spectrum, is not observed in the case of gravity waves. This difference in the effects of discretization of the spectrum on the weak turbulence of capillary waves and that of gravity waves is discussed in relation to the number of trios or quartets of component waves which satisfy the conditions for quasi-resonant nonlinear interactions. [Copyright &y& Elsevier]

A technique of calculating the frequency bias of an electric power system from frequency fluctuation data and total output power is described. An evaluation method for testing the calculations by the new method is developed. The results are in good agreement with estimates based on generator speed regulation but the method gives an excessively high figure for the load frequency bias. [ABSTRACT FROM AUTHOR]

Forward flights of a bilaterally symmetrically flapping butterfly modeled as a four-link rigid-body system consisting of a thorax, an abdomen, and left and right wings are numerically simulated. The joint motions of the butterflies are adopted from experimental observations. Three kinds of the simulations, distinguished by ways to determine the position and attitude of the thorax, are carried out: a tethered simulation, a prescribed simulation, and free-flight simulations. The upward and streamwise forces as well as the wake structures in the tethered simulation, where the thorax of the butterfly is fixed, reasonably agree with those in the corresponding tethered experiment. In the prescribed simulation, where the thoracic trajectories as well as the joint angles are given by those observed in a free-flight experiment, it is confirmed that the butterfly can produce enough forces to achieve the flapping flights. Moreover, coherent vortical structures in the wake and those on the wings are identified. The generation of the aerodynamic forces due to the vortical structures are also clarified. In the free-flight simulation, where only the joint angles are given as periodic functions of time, it is found that the free flight is longitudinally unstable because the butterfly cannot maintain the attitude in a proper range. Focusing on the abdominal mass, which largely varies owing to feeding and metabolizing, we have shown that the abdominal motion plays an important role in periodic flights. The necessity of control of the thoracic attitude for periodic flights and maneuverability is also discussed. [ABSTRACT FROM AUTHOR]

Vertical variation in leaf gas exchange characteristics of trees grown in a lowland dipterocarp forest in Peninsular Malaysia was investigated. Maximum net photosynthetic rate, stomatal conductance, and electron transport rate of leaves at the upper canopy, lower canopy, and forest floor were studied in situ with saturated condition photosynthetic photon flux density. The dark respiration rate of leaves at the various heights was also studied. Relationships among gas exchange characteristics, and also with nitrogen content per unit leaf area and leaf dry matter per area were clearly detected, forming general equations representing the vertical profile of several important parameters related to gas exchange. Numerical analysis revealed that the vertical distribution of gas exchange parameters was well determined showing both larger carbon gain for the whole canopy and at the same time positive carbon gain for the leaves of the lowest layer. For correct estimation of gas exchange at both leaf and canopy scales using multi-layer models, it is essential to consider the vertical distribution of gas exchange parameters with proper scaling coefficients. [ABSTRACT FROM AUTHOR]

The spectral energy density of the internal waves in the open ocean is considered. The Garrett and Munk spectrum and the resonant kinetic equation are used as the main tools of the study. Evaluations of a resonant kinetic equation that suggest the slow time evolution of the Garrett and Munk spectrum is not in fact slow are reported. Instead, nonlinear transfers lead to evolution time scales that are smaller than one wave period at high vertical wavenumber. Such values of the transfer rates are inconsistent with the viewpoint expressed in papers by C. H. McComas and P. Müller, and by P. Müller et al., which regards the Garrett and Munk spectrum as an approximate stationary state of the resonant kinetic equation. It also puts the self-consistency of a resonant kinetic equation at a serious risk. The possible reasons for and resolutions of this paradox are explored. Inclusion of near-resonant interactions decreases the rate at which the spectrum evolves. Consequently, this inclusion shows a tendency of improving of self-consistency of the kinetic equation approach. [ABSTRACT FROM AUTHOR]

The regulation of cue-induced craving for cigarettes is a key factor in smoking cessation. Outcomes of smoking cessation have been linked to self-efficacy, faith in one's own ability, in smokers. However, no study has examined the neural basis of self-efficacy during the control of craving. We examined whether self-efficacy can affect the neural response to smoking cues in smokers and ex-smokers using functional magnetic resonance imaging. During scanning, participants were instructed (1) to view smoking-related images passively, (2) to view the smoking-related images with a strategy focused on self-efficacy to control cue-induced craving or (3) to view neutral images. In smokers, the self-efficacy strategy significantly reduced self-reported craving. This strategy was related to increased activation in the rostral medial prefrontal cortex (rmPFC) and the pregenual anterior cingulate cortex in smokers compared with ex-smokers. Furthermore, smokers showed increased effective connectivity between rmPFC and hippocampus and between pregenual anterior cingulate cortex and parahippocampus gyrus when employing the self-efficacy strategy compared with ex-smokers. The magnitude of the rmPFC-hippocampus connectivity was positively correlated with self-reported self-efficacy. Our findings suggest that in smokers, self-efficacy is related to activation and connectivity in brain regions involved in regulating craving and self-assessment. The current study provides evidence for understanding the vunderlying cognitive and neurobiological mechanisms involved in the control of craving to smoke cigarettes. [ABSTRACT FROM AUTHOR]

Pathological gambling (PG) is characterized by continual repeated gambling behavior despite negative consequences. PG is considered to be a disorder of altered decision-making under risk, and behavioral economics tools were utilized by studies on decision-making under risk. At the same time, PG was suggested to be a heterogeneous disorder in terms of personality traits as well as risk attitude. We aimed to examine the heterogeneity of PG in terms of loss aversion, which means that a loss is subjectively felt to be larger than the same amount of gain. Thirty-one male PG subjects and 26 male healthy control (HC) subjects underwent a behavioral economics task for estimation of loss aversion and personality traits assessment. Although loss aversion in PG subjects was not significantly different from that in HC subjects, distributions of loss aversion differed between PG and HC subjects. HC subjects were uniformly classified into three levels (low, middle, high) of loss aversion, whereas PG subjects were mostly classified into the two extremes, and few PG subjects were classified into the middle range. PG subjects with low and high loss aversion showed a significant difference in anxiety, excitement-seeking and craving intensity. Our study suggested that PG was a heterogeneous disorder in terms of loss aversion. This result might be useful for understanding cognitive and neurobiological mechanisms and the establishment of treatment strategies for PG. [ABSTRACT FROM AUTHOR]

To investigate seasonal changes in the whole body content and tissue distribution of tetrodotoxin (TTX) in the pufferfish Takifugu niphobles , wild individuals were collected from the coastal waters around Miura Peninsula from November 2010 to May 2012, and their tissues were subjected to LC-MS/MS analysis. Fish that were sexually mature were classified as being in the maturation period (April), the spawning period (May–July) or the “ordinary period” (i.e., other months). In both sexes, gonad somatic index rapidly increased during the maturation period and then decreased during the spawning period. Whole body TTX content was significantly higher during the maturation/spawning period than in the ordinary period. Through all seasons, TTX was localized in the skin or ovary in females and in the skin or liver in males: the difference in TTX localization between females and males was particularly evident during the spawning period. [ABSTRACT FROM AUTHOR]

Abstract: Marine pufferfish contain tetrodotoxin (TTX), an extremely potent neurotoxin. All species of the genus Takifugu accumulate TTX in the liver and ovaries, although the tissue(s) in which it is localized can differ among species. TTX is the major defense strategy the pufferfish appears to use against predators. TTX is also used as a male-attracting pheromone during spawning. Here we demonstrate an additional (and unexpected) use of maternal TTX in the early larval stages of the Takifugu pufferfish. Predation experiments demonstrated that juveniles of all the species of fish used as predators ingested pufferfish larvae, but spat them out promptly. Liquid Chromatography-Tandem Mass Spectrometry (LC-MSMS) analysis revealed that the pufferfish larvae contain a small quantity of TTX, which is not enough to be lethal to the predators. Immunohistochemical analysis with anti-TTX monoclonal antibody revealed that the TTX is primarily localized in the body surface of the larvae as a layer of protection. Our study showed the female parent of the Takifugu pufferfish vertically transfers TTX to the larvae through its accumulation in the ovaries, and subsequent localization on the body surface of the larvae. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to clarify the principle of stabilization in flapping-of-wing flight of a butterfly, which is a rhythmic and cyclic motion. For this purpose, a dynamics model of a butterfly is derived by Lagrange’s method, where the butterfly is considered as a rigid multi-body system. For the aerodynamic forces, a panel method is applied. Validity of the mathematical models is shown by an agreement of the numerical result with the measured data. Then, periodic orbits of flapping-of-wing flights are searched in order to fly the butterfly models. Almost periodic orbits are obtained, but the model in the searched flapping-of-wing flight is unstable. This research, then, studies how the wake-induced flow and the flexibly torsional wing’s effect on the flight stability. Numerical simulations demonstrate that both the wake-induced flow and the flexible torsion reduces the flight instability. Because the obtained periodic flapping-of-wing flight is unstable, a feedback control system is designed, and a stable flight is realized. [Copyright &y& Elsevier]

Steady scale-invariant solutions of a kinetic equation describing the statistics of oceanic internal gravity waves based on wave turbulence theory are investigated. It is shown in the nonrotating scale-invariant limit that the collision integral in the kinetic equation diverges for almost all spectral power-law exponents. These divergences come from resonant interactions with the smallest horizontal wavenumbers and/or the largest horizontal wavenumbers with extreme scale separations. A small domain is identified in which the scale-invariant collision integral converges and numerically find a convergent power-law solution. This numerical solution is close to the Garrett--Munk spectrum. Power-law exponents that potentially permit a balance between the infrared and ultraviolet divergences are investigated. The balanced exponents are generalizations of an exact solution of the scale-invariant kinetic equation, the Pelinovsky--Raevsky spectrum. A small but finite Coriolis parameter representing the effects of rotation is introduced into the kinetic equation to determine solutions over the divergent part of the domain using rigorous asymptotic arguments. This gives rise to the induced diffusion regime. The derivation of the kinetic equation is based on an assumption of weak nonlinearity. Dominance of the nonlocal interactions puts the self-consistency of the kinetic equation at risk. However, these weakly nonlinear stationary states are consistent with much of the observational evidence. [ABSTRACT FROM AUTHOR]

We have recently taken care of a patient with QTc prolongation and Torsades des Pointes (TdP) resulting from an extreme overdose of eperisone, a centrally acting antispasmodic agent [[1]] commonly used in several Asian countries including Japan. Thus, the appearance of QTc prolongation indicates extremely high serum concentration and consequent half-life prolongation. [Extracted from the article]

The article presents information on the estimation of power frequency characteristics in power systems using spectral analysis techniques. Power-frequency characteristics are defined by a ratio of the power interrupted from the system to the frequency dropped at that time during the load interruption test of a power station, and have been measured. However, it is impossible using this test method to determine the system constant for each system, for each generator, and for each load, although it is possible to know the system constants of the entire interconnected systems. Moreover, power-frequency characteristics are determined by the configuration of loads and power stations as welt as the operation state of the power stations, and are changing instantaneously.