Does feedback temperature dependence influence the slow mode of the climate response?

Atmosphere-Ocean General Circulation models (AOGCMs) are a necessary tool to understand climate dynamics on centennial timescales for which observations are scarce. We explore to which degree the temperature dependence of the climate radiative feedback influences the slow mode of the surface temperature response. We question whether long-term climate change is described by a single e-folding mode with a constant timescale which is commonly assumed to be independent of temperature or forcing and the evolution of time. To do so, we analyze AOGCM simulations which have an integration time of 1000 years and are forced by atmospheric CO2 concentrations ranging from 2 times (2X) to 8 times (8X) the preindustrial level. Our findings suggest that feedback temperature dependence strongly influences the equilibrium temperature response and adjustment timescale of the slow mode. The magnitude and timescale of the slow mode is approximately reproduced by a zero-dimensional energy balance model that has a constant effective heat capacity and incorporates a background feedback parameter and a coefficient for feedback temperature dependence. However, the effective heat capacity of the slow mode increases over time, which makes the adjustment timescale also time-dependent. The time-varying adjustment timescale can be approximated by a multiple timescale structure of the slow temperature response, or vice versa, a multiple timescale structure of the slow temperature response is described by a time-dependent timescale. The state-dependence and time-dependence of the adjustment timescale of long-term climate change puts into question common eigenmode decomposition with a fast and a slow timescale in the sense that the slow mode is not well described by a single linear e-folding mode with a constant timescale. We find that such an eigenmode decomposition is valid at a certain forcing level only, and an additional mode or a multiple mode and timescale structure of the slow adjustment is necessary to reproduce the details of AOGCM simulated long-term climate change.

Bifurcated Current Sheet Observed on the Boundary of Kelvin-Helmholtz Vortices

On May 5, 2017 MMS observed a bifurcated current sheet at the boundary of Kelvin-Helmholtz vortices (KHVs) developed on the dawnside tailward magnetopause. We use the event to enhance our understanding of the formation and structure of asymmetric current sheets in the presence of density asymmetry, flow shear, and guide field, which have been rarely studied. The entire current layer comprises three separate current sheets, each corresponding to magnetosphere-side sunward separatrix region, central near-X-line region, and magnetosheath-side tailward separatrix region. Two off-center structures are identified as slow-mode discontinuities. All three current sheets have a thickness of ∼0.2 ion inertial length, demonstrating the sub-ion-scale current layer, where electrons mainly carry the current. We find that both the diamagnetic and electron anisotropy currents substantially support the bifurcated currents in the presence of density asymmetry and weak velocity shear. The combined effects of strong guide field, low density asymmetry, and weak flow shear appear to lead to asymmetries in the streamlines and the current-layer structure of the quadrupolar reconnection geometry. We also investigate intense electrostatics waves observed on the magnetosheath side of the KHV boundary. These waves may pre-heat a magnetosheath population that is to participate into the reconnection process, leading to two-step energization of the magnetosheath plasma entering into the magnetosphere via KHV-driven reconnection.

A combination of notch signaling, preferential adhesion and endocytosis induces a slow mode of cell intercalation in the Drosophila retina

Movement of epithelial cells in a tissue occurs through neighbor exchange and drives tissue shape changes. It requires intercellular junction remodeling, a process typically powered by the contractile actomyosin cytoskeleton. This has mostly been investigated in homogeneous epithelia where intercalation takes minutes. However, in some tissues, intercalation involves different cell types and can take hours. Whether slow and fast intercalation share the same mechanisms remains to be examined. To address this issue, we use the fly eye, where the cone cells exchange neighbors over approximately 10 hours to shape the lens. We uncover three pathways regulating this slow mode of cell intercalation. Firstly, we find a limited requirement for MyosinII. In this case, mathematical modeling predicts an adhesion dominant intercalation mechanism. Genetic experiments support this prediction and reveal a role for adhesion through the Nephrin proteins Roughest and Hibris. Secondly, we find cone cell intercalation is regulated by the Notch-signaling pathway. Thirdly, we show endocytosis is required for membrane removal and Notch activation. Altogether, our work indicates that adhesion, endocytosis and Notch can induce junction remodeling over long-time scales.

The Formation and Decay of an Unstable State of a Suspension of Hydrophobic Nanoporous Particles under Rapid Compression

The study of non-wetting liquid transport in a nanoporous medium is stimulated by the possible use of this process to absorb or accumulate mechanical energy. The filling of nanopores of suspended particles with a non-wetting liquid under decay of the unstable state, when the pressure increase rate is much higher than the rate of volume change, is studied. Based on the new experimental data and a theoretical model of the interacting modes of the spontaneous filling and filling under rapid compression, a picture of the percolation transition and a mechanism of liquid transport under such conditions are proposed. It is shown that a new dynamic filling threshold P0 is reached. It is shown that the filling of the porous medium is the result of the slow mode of impact compression when the fast mode of spontaneous filling is continuously adjusted to the slow mode on a small time scale. The theoretical model of the interacting modes is based on the solving of a system of kinetic equations for the distribution functions f(n,t) and F(n,t) clusters of filled pores under rapid compression, respectively. It is shown that filling at P=const corresponds to the non-dissipative transport of liquid on a time scale smaller than the characteristic filling time. The proposed model quantitatively describes the experimental data. So, the response of suspension to impact is characterized by the positive feedback.

Islamic Financing for Small Medium Enterprises: Challenges and Opportunities

This study attempts to discuss the challenges and opportunities of Islamic financing for Small Medium Enterprise (SMEs), as the Islamic finance industry's growth and SMEs are stimulated in this recent year. The government has introduced Islamic SME financing since 2012, and Malaysia has promoted it by granting a rebate for the participated parties, especially Islamic financial institutions. However, the government's opportunities are still in the slow mode to be grabbed by SMEs. With selected literature related to SMEs and Islamic financing, this study discussed SMEs and Islamic banks' practices in Malaysia. Based on the literature, several issues had to be highlighted, such as SMEs' readiness to have the opportunity with larger firms, SMEs' behaviours, and attitudes when dealing with external supports, as well as their awareness of business financing. Thus, this study highlights the challenges and real issues among SMEs and points out the opportunities for improvement that are expected to benefit SMEs and Islamic financial institutions in Malaysia.