Time Dependent
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2021 ◽  
Vol 7 (49) ◽  
Author(s):  
Paolo D’Imporzano ◽  
Katrien Keune ◽  
Janne M. Koornneef ◽  
Erma Hermens ◽  
Petria Noble ◽  
...  

2021 ◽  
Vol 9 (12) ◽  
pp. 1362
Author(s):  
Xiaolong Zong ◽  
Ruzhen Zhang ◽  
Shuwen Zhang ◽  
Fangjing Deng ◽  
Wei Zhou ◽  
...  

In the background of global warming and climate change, nuisance flooding is only caused by astronomical tides, which could be modulated by the nodal cycle. Therefore, much attention should be paid to the variation in the amplitude of the nodal cycle. In this paper, we utilize the enhanced harmonic analysis method and the independent point scheme to obtain the time-dependent amplitudes of the 8.85-year cycle of N2 tide and the 4.42-year cycle of 2N2 tide based on water level records of four tide gauges in the Gulf of Maine. Results indicate that the long-term trends of N2 and 2N2 tides vary spatially, which may be affected by the sea-level rise, coastal defenses, and other possible climate-related mechanisms. The comparison between Halifax and Eastport reveals that the topography greatly influences the amplitudes of those cycles. Moreover, a quasi 20-year oscillation is obvious in the 8.85-year cycle of N2 tide. This oscillation probably relates to a 20-year mode in the North Atlantic Ocean.


2021 ◽  
Vol 932 ◽  
Author(s):  
Qingyun Zeng ◽  
Hongjie An ◽  
Claus-Dieter Ohl

We study systematically the cavitation-induced wall shear stress on rigid boundaries as a function of liquid viscosity $\mu$ and stand-off distance $\gamma$ using axisymmetric volume of fluid (VoF) simulations. Here, $\gamma =d/R_{max}$ is defined with the initial distance of bubble centre from the wall $d$ and the bubble equivalent radius at its maximum expansion $R_{max}$ . The simulations predict accurately the overall bubble dynamics and the time-dependent liquid film thickness between the bubble and the wall prior to the collapse. The spatial and temporal wall shear stress is discussed in detail as a function of $\gamma$ and the inverse Reynolds number $1/Re$ . The amplitude of the wall shear stress is investigated over a large parameter space of viscosity and stand-off distance. The inward stress is caused by the shrinking bubble and its maximum value $\tau _{mn}$ follows $\tau _{mn} Re^{0.35}=-70\gamma +110$ (kPa) for $0.5<\gamma <1.4$ . The expanding bubble and jet spreading on the boundary produce an outward-directed stress. The maximum outward stress is generated shortly after impact of the jet during the early spreading. We find two scaling laws for the maximum outward stress $\tau _{mp}$ with $\tau _{mp} \sim \mu ^{0.2} h_{jet}^{-0.3} U_{jet}^{1.5}$ for $0.5\leq \gamma \leq 1.1$ and $\tau _{mp} \sim \mu ^{-0.25} h_{jet}^{-1.5} U_{jet}^{1.5}$ for $\gamma \geq 1.1$ , where $U_{jet}$ is the jet impact velocity and $h_{jet}$ is the distance between lower bubble interface and wall prior to impact.


2021 ◽  
Vol 9 ◽  
Author(s):  
A. Auzemery ◽  
E. Willingshofer ◽  
P. Yamato ◽  
T. Duretz ◽  
F. Beekman

We perform numerical modelling to simulate the shortening of an oceanic basin and the adjacent continental margins in order to discuss the relationship between compressional stresses acting on the lithosphere and the time dependent strength of the mid-oceanic ridges within the frame of subduction initiation. We focus on the role of stress regulating mechanisms by testing the stress–strain-rate response to convergence rate, and the thermo-tectonic age of oceanic and continental lithospheres. We find that, upon compression, subduction initiation at passive margin is favoured for thermally thin (Palaeozoic or younger) continental lithospheres (&lt;160 km) over cratons (&gt;180 km), and for oceanic basins younger than 60 Myr (after rifting). The results also highlight the importance of convergence rate that controls stress distribution and magnitudes in the oceanic lithosphere. Slow convergence (&lt;0.9 cm/yr) favours strengthening of the ridge and build-up of stress at the ocean-continent transition allowing for subduction initiation at passive margins over subduction at mid-oceanic ridges. The results allow for identifying geodynamic processes that fit conditions for subduction nucleation at passive margins, which is relevant for the unique case of the Alps. We speculate that the slow Africa–Europe convergence between 130 and 85 Ma contributes to the strengthening of the mid-oceanic ridge, leading to subduction initiation at passive margin 60–70 Myr after rifting and passive margin formation.


2021 ◽  
Author(s):  
Kayla E. Rohr ◽  
Thomas Inda ◽  
Jennifer A. Evans

Circadian rhythms in behavior and physiology are programmed by the suprachiasmatic nucleus (SCN) of the hypothalamus. A subset of SCN neurons produce the neuropeptide arginine vasopressin (AVP), but it remains unclear whether AVP signaling influences the SCN clock directly. Here we test that AVP signaling acting through V1A and V1B receptors influences molecular rhythms in SCN neurons. V1 receptor agonists were applied ex vivo to PERIOD2::LUCIFERASE SCN slices, allowing for real-time monitoring of changes in molecular clock function. V1A/B agonists reset the phase of the SCN molecular clock in a time-dependent manner, with larger magnitude responses by the female SCN. Further, we find evidence that both Gq and Gs signaling pathways interact with V1A/B-induced SCN resetting, and that this response requires vasoactive intestinal polypeptide (VIP) signaling. Collectively, this work indicates that AVP signaling resets SCN molecular rhythms in conjunction with VIP signaling and in a manner influenced by sex. This highlights the utility of studying clock function in both sexes and suggests that signal integration in central clock circuits regulates emergent properties important for the control of daily rhythms in behavior and physiology.


2021 ◽  
Vol 36 (4) ◽  
pp. 718-744
Author(s):  
Khaled Mokni ◽  
Mohamed Sahbi Nakhli ◽  
Othman Mnari ◽  
Khemaies Bougatef

This study examines the causal relationships between oil prices and the MSCI stock index of G7 countries between September 2004 and October 2020. This study is novel in implementing symmetric and asymmetric time-varying causality tests based on the bootstrap rolling-window approach. The results reveal that the causal link between oil prices and G7 stock markets is time-dependent. The periods of bidirectional causality roughly coincide with the global financial crisis and the ongoing COVID-19 pandemic. When asymmetry is accounted for, the results suggest an asymmetric causality between the two markets expressed by different patterns regarding positive and negative oil shocks. The results also indicate symmetric causality during the COVID-19 pandemic. These findings have implications for portfolio design and hedging strategies that are important to both policymakers and investors.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fabio Vanni ◽  
David Lambert ◽  
Luigi Palatella ◽  
Paolo Grigolini

AbstractThe reproduction number of an infectious disease, such as CoViD-19, can be described through a modified version of the susceptible-infected-recovered (SIR) model with time-dependent contact rate, where mobility data are used as proxy of average movement trends and interpersonal distances. We introduce a theoretical framework to explain and predict changes in the reproduction number of SARS-CoV-2 in terms of aggregated individual mobility and interpersonal proximity (alongside other epidemiological and environmental variables) during and after the lockdown period. We use an infection-age structured model described by a renewal equation. The model predicts the evolution of the reproduction number up to a week ahead of well-established estimates used in the literature. We show how lockdown policies, via reduction of proximity and mobility, reduce the impact of CoViD-19 and mitigate the risk of disease resurgence. We validate our theoretical framework using data from Google, Voxel51, Unacast, The CoViD-19 Mobility Data Network, and Analisi Distribuzione Aiuti.


Author(s):  
M. Naveed ◽  
Z. Abbas ◽  
M. Imran

The main objective of the present article is to provide an analytical simulation for time dependent boundary layer flow of non-Newtonian Williamson fluid due to stretchable curved oscillatory Riga surface. Also the characteristics of heat and mass transport are studied under the influence of variable thermal conductivity and diffusivity along with convective heat and mass boundary conditions. Additionally, energy equation is also characterized with the impact of heat production. Curvilinear coordinate scheme is followed to attain the boundary layer expressions for the flow model. The governing nonlinear partial differential equations are solved analytically via homotopy analysis method (HAM). Graphs are plotted to examine comprehensively the consequences of various concerned parameters like modified magnetic parameter and radius of curvature, Williamson fluid parameter, relation of the surface's oscillating frequency to its stretching rate constant, Prandtl number, variable conductivity and heat production parameters, Schmidt number and variable diffusivity parameter on concentration, temperature, pressure and velocity profile. Also the outcomes of afore said variables on surface drag force, rate of temperature and mass transmission (Nusselt and Sherwood numbers) are shown in tabular form. The liquid velocity amplitude is enhanced with modified magnetic parameter and shows opposite behavior for Williamson fluid parameter.


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