Exit Function Research Articles

The system functions of direct democracy - a ranking of 103 countries in the world

We introduce a new framework of the functions of direct democracy within a democratic political system. These are: (1) channeling political input into the decision-making arenas by circumventing organized interests (input function), (2) channeling political issues out of the representative decision-making system (exit function), and (3) producing decisions about political questions (decision function). Based on the analysis of 277 instruments of direct democracy on the national level in 103 countries around the world, we find that the input and exit functions are rather unbalanced in their dynamics. The exit function shows a tendency to strengthen the concentration of power, whereas the input function rarely allows for access to both decision-making arenas. However, once issues reach the referendum, the impact is often strong, and only a small minority of states conduct referendums without any formal consequences. Beyond these results, the presented approach allows to start long-time observations of the state of direct democracy in democratic systems.

Research on Dynamic Gesture Recognition and Control System based on Machine Vision

Hand gesture recognition and control is a new type of human-computer interaction that can provide a more convenient and efficient operation mode by utilizing non-contact gesture recognition technology. This paper presents a lightweight dynamic gesture recognition method for intelligent office presentation control. First, we introduce the concept of hand gesture recognition and go over key gesture recognition technologies like classification. The structure, process, and evaluation index of the gesture recognition algorithm are described in detail using a convolutional neural network model. During the experiment's algorithm verification phase, we test and analyze the algorithm using the Python language, compilation environment, and data set. In the control experiment, we evaluated the system's ability to control the office application's start, play, next, previous, and exit functions. We achieve 96.3% accuracy on the test set. Experimental results show that the system can recognize a wide range of hand gestures and accurately control the presentation.

Dynamics of a Class of Prey–Predator Models with Singular Perturbation and Distributed Delay

In this paper, two prey–predator models with distributed delays are presented based on the growth and loss rates of the predator, which are much smaller than that of the prey, leading to a singular perturbation problem. It is obtained that Hopf bifurcation can occur, where the coexistence equilibrium becomes unstable leading to a stable limit cycle. Subsequently, considering the perturbation parameter [Formula: see text], the fact that the solution crossing the transcritical point converges to a stable equilibrium is discussed for the model with Holling type I using the linear chain criterion, center-manifold reduction, the geometric singular perturbation theory and entry–exit function. The existence and uniqueness of relaxation oscillation cycle for the model with Holling type II are obtained. In addition, numerical simulations are provided to verify the analytical results.

Network-Wide Implementation of Roundabouts Versus Signalized Intersections on Urban Streets: Analytical and Simulation Comparison

This paper examines the impact of roundabouts implemented at intersections throughout a dense urban network on its operational performance. Metrics considered include the average free-flow speed, flow-moving capacity, trip-serving capacity, and fuel consumption rate. Three intersection strategies are compared: signalized intersections allowing left turns in a permitted manner (TWs), signalized intersections prohibiting left turns (TWLs), and modern roundabouts (RBs). Using the approaches of macroscopic fundamental diagrams and network exit functions, both analytical investigations and microscopic traffic simulations for grid networks were conducted. In general, the results from both analyses agree well. The results reveal that when single-lane roundabouts are applied in networks with a single travel in each direction, the RB network outperforms the TW network for all operational metrics. The RB network also outperforms the TWL network in free-flow speed and flow-moving capacity and has a similar trip-serving capacity as the TWL network. However, when roundabouts with two travel lanes are applied on multi-lane networks, the TWL network exceeds the RB network in both flow-moving and trip-serving capacities. This decrease in the performance of the RB network could possibly come from the complexity imposed on the entering vehicle that wants to use the inner lane. Moreover, because vehicles in the RB network need to accelerate/decelerate more frequently those in the other networks, the RB network generates a higher fuel consumption rate in uncongested and capacity conditions. The findings suggest intersections of roundabouts could be beneficial for networks with a single travel lane in each direction.

Slow–fast dynamics in a neurotransmitter release model: Delayed response to a time-dependent input signal

We propose a generalization of the neurotransmitter release model proposed in Rodrigues et al. (2016). We increase the complexity of the underlying slow–fast system by considering a degree-four polynomial as parametrization of the critical manifold. We focus on the possible transient and asymptotic dynamics, exploiting the so-called entry–exit function to describe slow parts of the dynamics. We provide extensive numerical simulations, complemented by numerical bifurcation analysis.

Coexistence of one predator and two prey through rapid evolution in predator’s feeding choice

In this article, we study the coexistence of one predator and two prey with evolutionary effects. To that end, we formulate a three-time-scale model with rapid adaptive in predator’s feeding choice, slow prey growth and superslow predator growth. By using the geometric singular perturbation theory and computing the entry–exit function for multidimensional fast–slow systems, we find that the predator and the two prey coexist in a form of relaxation oscillations between being near the extreme values of feeding choice strategy due to the associated delay of stability loss. It is also found that the predator can coexist with the two prey in the form of an interior equilibrium with a locally optimal feeding choice.

Entry–Exit Functions in Fast–Slow Systems with Intersecting Eigenvalues

AbstractWe study delayed loss of stability in a class of fast–slow systems with two fast variables and one slow one, where the linearisation of the fast vector field along a one-dimensional critical manifold has two real eigenvalues which intersect before the accumulated contraction and expansion are balanced along any individual eigendirection. That interplay between eigenvalues and eigendirections renders the use of known entry–exit relations unsuitable for calculating the point at which trajectories exit neighbourhoods of the given manifold. We illustrate the various qualitative scenarios that are possible in the class of systems considered here, and we propose novel formulae for the entry–exit functions that underlie the phenomenon of delayed loss of stability therein.

Opposing Hysteresis Patterns in Flow and Outflow Macroscopic Fundamental Diagrams and Their Implications

Two key aggregated traffic models are the relationship between average network flow and density (known as the network or flow macroscopic fundamental diagram [flow-MFD]) and the relationship between trip completion and density (known as network exit function or the outflow-MFD [o-FMD]). The flow- and o-MFDs have been shown to be related by average network length and average trip distance under steady-state conditions. However, recent studies have demonstrated that these two relationships might have different patterns when traffic conditions are allowed to vary: the flow-MFD exhibits a clockwise hysteresis loop, while the o-MFD exhibits a counter-clockwise loop. One recent study attributes this behavior to the presence of bottlenecks within the network. The present paper demonstrates that this phenomenon may arise even without bottlenecks present and offers an alternative, but more general, explanation for these findings: a vehicle’s entire trip contributes to a network’s average flow, while only its end contributes to the trip completion rate. This lag can also be exaggerated by trips with different lengths, and it can lead to other patterns in the o-MFD such as figure-eight patterns. A simple arterial example is used to demonstrate this explanation and reveal the expected patterns, and they are also identified in real networks using empirical data. Then, simulations of a congestible ring network are used to unveil features that might increase or diminish the differences between the flow- and o-MFDs. Finally, more realistic simulations are used to confirm that these behaviors arise in real networks.

Relaxation Oscillations and Dynamical Properties in a Time Delay Slow–Fast Predator–Prey Model with a Piecewise Smooth Functional Response

In the past few decades, the predator–prey model has played an important role in the dynamic behavior of populations. Many scholars have studied the stability of the predator–prey system. Due to the complex influence of time delay on the dynamic behavior of systems, time-delay systems have garnered wide interest. In this paper, a classical piecewise smooth slow–fast predator–prey model is considered. The dynamic properties of the system are analyzed by linearization. The existence and uniqueness of the relaxation oscillation are then proven through the geometric singular perturbation theory and entry–exit function. Finally, a stable limit cycle is obtained. A numerical simulation verifies our results for the systems and shows the effectiveness of the method in dealing with time delays.

Relaxation oscillations in a slow–fast predator–prey model with weak Allee effect and Holling-IV functional response

By using geometric singular perturbation theory and a new entry–exit function, this paper is concerned with the number and stability of relaxation oscillations in a slow–fast predator–prey model with weak Allee effect and Holling-IV functional response. We find that this model can admit at most three nested (large amplitude) relaxation oscillations. Two of them are stable while the other one is unstable. Also we find that the relative heights between the folded points and the transcritical bifurcation point of the critical curves affect the number and stability of relaxation oscillations greatly. Compared with the existing models, the weak Allee effect makes the model possess one more sustained oscillations, i.e., the weak Allee effect promotes the stability of the predator–prey system. The theoretical predictions about the number and stability of relaxation oscillations are verified by numerical simulations.

The Arabidopsis STE20/Hippo kinase SIK1 regulates polarity independently of PIN proteins

Polarity is a feature of life. In higher plants, non-autonomous polarity is largely directed by auxin, the morphogen that drives its own polarized flow, Polar Auxin Transport (PAT), to guide patterning events such as phyllotaxis and tropism. The plasma membrane-localized PIN-FORMED (PIN) auxin efflux carriers are rate-limiting factors in PAT. In yeasts and metazoans, the STE20 kinases are key players in cell polarity. We had previously characterized SIK1 as a STE20/Hippo orthologue in Arabidopsis and confirmed its function in mitotic exit and organ growth. Here we explore the possible link between SIK1, auxin, PIN, and polarity. Abnormal phyllotaxis and gravitropism were observed in sik1. sik1 was more sensitive to exogenous auxin in primary root elongation and lateral root emergence. RNA-Seq revealed reduced expression in auxin biosynthesis genes and induced expression of auxin flux carriers in sik1. However, normal tissue- and sub-cellular localization patterns of PIN1 and PIN2 were observed in sik1. The dark-induced vacuolar degradation of PIN2 also appeared normal in sik1. An additive phenotype was observed in the sik1 pin1 double mutant, indicating that SIK1 does not directly regulate PIN1. The polarity defects of sik1 are hence unlikely mediated by PINs and await future exploration.

An OpenCV Tool for Data Logging by Face Recognition

The human face contains various features and characteristics, which is not unique for two humans. Each human has different identity. Face recognition is an identification system that uses the characteristics of a person’s face to obtain the person's identity . The human face recognition process consists of two stages: face detection, here the camera detects that there is a face in front of it; this process is rapid in humans and the next is recognizing or identifying that face among a group of people. The recognition stage is mostly worked upon to develop models for facial recognitions. This paper presents a new method used to detect and recognize the face in real-time environment using Raspberry Pi and Python. The system uses a camera that will be able to detect the human face, auto counter and log into the system. A single portal is used for a human’s data Entry and Exit. These Entry and Exit functions are triggered by GUI. The information of the members are stored in a Spreadsheets are used in this paper. In this paper LBP histograms is used for face recognition and a modified algorithm of Haar’s Cascades is used for face detection..

Septin clearance from the division site triggers cytokinesis in budding yeast.

In many eukaryotic cells cytokinesis involves a contractile actomyosin ring (CAR) that drives cleavage furrow ingression. What triggers CAR constriction at a precise time of the cell cycle and how constriction is coupled to chromosome segregation are fundamental questions. In the budding yeast Saccharomyces cerevisiae, CAR assembly strictly requires a rigid septin collar that forms at the bud neck early during the cell cycle. At the time of cytokinesis, a sudden remodelling of the septin collar occurs, leading to its splitting into two separate rings that sandwich the CAR. We have shown that septin displacement during splitting is an essential prerequisite for CAR constriction [Tamborrini et al., Nat Commun. 9(1):4308]. Thus, cytokinesis in budding yeast is a two-step mechanism: during the first step, the septin collar organizes the assembly of the cytokinetic machinery at the right place while restraining CAR-driven membrane ingression; during the second step, a confined eviction of septins from the division site during septin ring splitting triggers CAR constriction. Our data further indicate that septin ring splitting is prompted by the Mitotic Exit Network (MEN), and in particular by its downstream phosphatase Cdc14, independently of its mitotic exit function. Surprisingly, MEN signalling at spindle pole bodies (SPBs) is critical for septin ring splitting and cytokinesis. Ubiquitination of the MEN anchor at SPBs by the Dma1/2 ubiquitin ligase attenuates MEN signalling and could have a decisive role in coupling cytokinesis to chromosome and organelle segregation. Altogether, our data emphasize the importance of septin ring splitting, which has been mysterious so far, and highlight a novel mechanism to prevent CAR constriction and cytokinesis in unpropitious conditions.

Budding Yeast BFA1 Has Multiple Positive Roles in Directing Late Mitotic Events.

The proper regulation of cell cycle transitions is paramount to the maintenance of cellular genome integrity. In Saccharomyces cerevisiae, the mitotic exit network (MEN) is a Ras-like signaling cascade that effects the transition from M phase to G1 during the cell division cycle in budding yeast. MEN activation is tightly regulated. It occurs during anaphase and is coupled to mitotic spindle position by the spindle position checkpoint (SPoC). Bfa1 is a key component of the SPoC and functions as part of a two-component GAP complex along with Bub2. The GAP activity of Bfa1-Bub2 keeps the MEN GTPase Tem1 inactive in cells with mispositioned spindles, thereby preventing inappropriate mitotic exit and preserving genome integrity. Interestingly, a GAP-independent role for Bfa1 in mitotic exit regulation has been previously identified. However the nature of this Bub2-independent role and its biological significance are not understood. Here we show that Bfa1 also activates the MEN by promoting the localization of Tem1 primarily to the daughter spindle pole body (dSPB). We demonstrate that the overexpression of BFA1 is lethal due to defects in Tem1 localization, which is required for its activity. In addition, our studies demonstrate a Tem1-independent role for Bfa1 in promoting proper cytokinesis. Cells lacking TEM1, in which the essential mitotic exit function is bypassed, exhibit cytokinesis defects. These defects are suppressed by the overexpression of BFA1. We conclude that Bfa1 functions to both inhibit and activate late mitotic events.

Relaxation oscillations in a slow–fast modified Leslie–Gower model

In this paper, we prove the existence and uniqueness of relaxation oscillation cycle of a slow–fast modified Leslie–Gower model via the entry–exit function and geometric singular perturbation theory. Numerical simulations are also carried out to illustrate our theoretical result.

Duality of Channels and Codes

For any given channel $W$ with classical inputs and possibly quantum outputs, a dual classical-input channel $W^\perp$ can be defined by embedding the original into a channel $\mathcal N$ with quantum inputs and outputs. Here we give new uncertainty relations for a general class of entropies that lead to very close relationships between the original channel and its dual. Moreover, we show that channel duality can be combined with duality of linear codes, whereupon the uncertainty relations imply that the performance of a given code over a given channel is entirely characterized by the performance of the dual code on the dual channel. This has several applications. In the context of polar codes, it implies that the rates of polarization to ideal and useless channels must be identical. Duality also relates the tasks of channel coding and privacy amplification, implying that the finite blocklength performance of extractors and codes is precisely linked, and that optimal rate extractors can be transformed into capacity-achieving codes, and vice versa. Finally, duality also extends to the EXIT function of any channel and code. Here it implies that for any channel family, if the EXIT function for a fixed code has a sharp transition, then it must be such that the rate of the code equals the capacity at the transition. This may give a different route to proving a code family achieves capacity by establishing sharp EXIT function transitions.

Numerical Modeling of Uniform Slab Brightness Coefficients based on the Mirror Reflection Principle and Linear Singular Integral Equations Solutions

Based on the mirror reflection principle and solutions of modified linear singular integral equations, the numerical modeling of the unified exit function of the outside radiation field and photometrical invariants of brightness coefficients for a uniform slab of finite optical thickness has been carried out. The efficacy of applying the angular discretization method for problems of numerical modeling of outer radiation fields in the «atmosphere — underlying surface» system has been proved. This new approach allows generalizing the basic results in the particular case of a semi-infinite uniform slab. In this connection the main mathematical aspects and computational peculiarity of the numerical realization of the angular discretization method have been considered. Due to linearity of the used basic integral equations, the conducted analysis can be generalized to the case of scalar and polarized inner radiation fields taking into account the multiple anisotropic scattering of photons and their reflection from an arbitrary horizontally uniform underlying surface.

Re-examining the role of Cdc14 phosphatase in reversal of Cdk phosphorylation during mitotic exit.

Inactivation of cyclin-dependent kinase (Cdk) and reversal of Cdk phosphorylation are universally required for mitotic exit. In budding yeast (Saccharomyces cerevisiae), Cdc14 is essential for both and thought to be the major Cdk-counteracting phosphatase. However, Cdc14 is not required for mitotic exit in many eukaryotes, despite highly conserved biochemical properties. The question of how similar enzymes could have such disparate influences on mitotic exit prompted us to re-examine the contribution of budding yeast Cdc14. By using an auxin-inducible degron, we show that severe Cdc14 depletion has no effect on the kinetics of mitotic exit and bulk Cdk substrate dephosphorylation, but causes a cell separation defect and is ultimately lethal. Phosphoproteomic analysis revealed that Cdc14 is highly selective for distinct Cdk sites in vivo and does not catalyze widespread Cdk substrate dephosphorylation. We conclude that additional phosphatases likely contribute substantially to Cdk substrate dephosphorylation and coordination of mitotic exit in budding yeast, similar to in other eukaryotes, and the critical mitotic exit functions of Cdc14 require trace amounts of enzyme. We propose that Cdc14 plays very specific, and often different, roles in counteracting Cdk phosphorylation in all species.

A New Methodology for the Quantification of In Vivo Cdc14 Phosphatase Activity.

The phosphatase Cdc14 has a pivotal function in the mitotic exit of Saccharomyces cerevisiae. During interphase, Cdc14 remains inactive in the nucleolus bound to the inhibitor Net1. Cdc14 activation occurs in the metaphase to anaphase transition and it is promoted by at least two signaling pathways called FEAR (CdcFourteen Early Anaphase Release) and MEN (Mitotic Exit Network). These two pathways act in parallel and target the phosphorylation of Net1, thus decreasing Net1 affinity for Cdc14. The activity of Cdc14 can be used as a readout to assay functional interactions of different components of the mitotic exit signaling pathways.

Mitotic Exit Function of Polo-like Kinase Cdc5 Is Dependent on Sequential Activation by Cdk1.

To complete mitosis, Saccharomyces cerevisiae needs to activate the mitotic phosphatase Cdc14. Two pathways contribute to Cdc14 regulation: FEAR (Cdc14 early anaphase release) and MEN (mitotic exit network). Cdc5 polo-like kinase was found to be an important mitotic exit component. However, its specific role in mitotic exit regulation and its involvement in Cdc14 release remain unclear. Here, we provide insight into the mechanism by which Cdc5 contributes to the timely release of Cdc14. Our genetic and biochemical data indicate that Cdc5 acts in parallel with MEN during anaphase. This MEN-independent Cdc5 function requires active separase and activation by Cdk1-dependent phosphorylation. Cdk1 first phosphorylates Cdc5 to activate it in early anaphase, and then, in late anaphase, further phosphorylation of Cdc5 by Cdk1 is needed to promote its MEN-related functions.